Namespace and ClassPath rewrites

Core/Driver/Logger/Logger.class.php

@@ -0,0 +1,126 @@
+<?php
+
+namespace Core\Driver\Logger;
+
+use Core\Driver\SQL\SQL;
+
+class Logger {
+
+  public const LOG_FILE_DATE_FORMAT = "Y-m-d_H-i-s_v";
+  public const LOG_LEVELS = [
+    0 => "debug",
+    1 => "info",
+    2 => "warning",
+    3 => "error",
+    4 => "severe"
+  ];
+
+  public static Logger $INSTANCE;
+
+  private ?SQL $sql;
+  private string $module;
+
+  // unit tests
+  private bool $unitTestMode;
+  private ?string $lastMessage;
+  private ?string $lastLevel;
+
+  public function __construct(string $module = "Unknown", ?SQL $sql = null) {
+    $this->module = $module;
+    $this->sql = $sql;
+    $this->unitTestMode = false;
+    $this->lastMessage = null;
+    $this->lastLevel = null;
+  }
+
+  protected function getStackTrace(int $pop = 2): string {
+    $debugTrace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+    if ($pop > 0) {
+      array_splice($debugTrace, 0, $pop);
+    }
+    return implode("\n", array_map(function ($trace) {
+      if (isset($trace["file"])) {
+        return $trace["file"] . "#" . $trace["line"] . ": " . $trace["function"] . "()";
+      } else {
+        return $trace["function"] . "()";
+      }
+    }, $debugTrace));
+  }
+
+  public function log(string $message, string $severity, bool $appendStackTrace = true) {
+
+    if ($appendStackTrace) {
+      $message .= "\n" . $this->getStackTrace();
+    }
+
+    $this->lastMessage = $message;
+    $this->lastLevel = $severity;
+    if ($this->unitTestMode) {
+      return;
+    }
+
+    if ($this->sql !== null && $this->sql->isConnected()) {
+      $success = $this->sql->insert("SystemLog", ["module", "message", "severity"])
+        ->addRow($this->module, $message, $severity)
+        ->execute();
+      if ($success !== false) {
+        return;
+      }
+    }
+
+    // database logging failed, try to log to file
+    $module = preg_replace("/[^a-zA-Z0-9-]/", "-", $this->module);
+    $date = (\DateTime::createFromFormat('U.u', microtime(true)))->format(self::LOG_FILE_DATE_FORMAT);
+    $logFile = implode("_", [$module, $severity, $date]) . ".log";
+    $logPath = implode(DIRECTORY_SEPARATOR, [WEBROOT, "core", "Logs", $logFile]);
+    @file_put_contents($logPath, $message);
+  }
+
+  public function error(string $message): string {
+    $this->log($message, "error");
+    return $message;
+  }
+
+  public function severe(string $message): string {
+    $this->log($message, "severe");
+    return $message;
+  }
+
+  public function warning(string $message): string {
+    $this->log($message, "warning", false);
+    return $message;
+  }
+
+  public function info(string $message): string {
+    $this->log($message, "info", false);
+    return $message;
+  }
+
+  public function debug(string $message, bool $appendStackTrace = false): string {
+    $this->log($message, "debug", $appendStackTrace);
+    return $message;
+  }
+
+  public static function instance(): Logger {
+    if (self::$INSTANCE === null) {
+      self::$INSTANCE = new Logger("Global");
+    }
+
+    return self::$INSTANCE;
+  }
+
+  public function getLastMessage(): ?string {
+    return $this->lastMessage;
+  }
+
+  public function getLastLevel(): ?string {
+    return $this->lastLevel;
+  }
+
+  /**
+   * Calling this method will prevent the logger from persisting log messages (writing to database/file),
+   */
+  public function unitTestMode() {
+    $this->unitTestMode = true;
+  }
+}

Core/Driver/SQL/Column/BigIntColumn.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class BigIntColumn extends IntColumn {
+
+  public function __construct(string $name, bool $nullable, $defaultValue, bool $unsigned) {
+    parent::__construct($name, $nullable, $defaultValue, $unsigned);
+    $this->type = "BIGINT";
+  }
+}

Core/Driver/SQL/Column/BoolColumn.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class BoolColumn extends Column {
+
+  public function __construct(string $name, bool $defaultValue = false) {
+    parent::__construct($name, false, $defaultValue);
+  }
+
+}

Core/Driver/SQL/Column/Column.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+use Core\Driver\SQL\Expression\Expression;
+
+class Column extends Expression {
+
+  private string $name;
+  private bool $nullable;
+  private $defaultValue;
+
+  public function __construct(string $name, bool $nullable = false, $defaultValue = NULL) {
+    $this->name = $name;
+    $this->nullable = $nullable;
+    $this->defaultValue = $defaultValue;
+  }
+
+  public function getName(): string { return $this->name; }
+  public function notNull(): bool { return !$this->nullable; }
+  public function getDefaultValue() { return $this->defaultValue; }
+
+}

Core/Driver/SQL/Column/DateTimeColumn.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class DateTimeColumn extends Column {
+
+  public function __construct(string $name, bool $nullable = false, $defaultValue = NULL) {
+    parent::__construct($name, $nullable, $defaultValue);
+  }
+}

Core/Driver/SQL/Column/DoubleColumn.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class DoubleColumn extends NumericColumn {
+  public function __construct(string $name, bool $nullable, $defaultValue = NULL, ?int $totalDigits = null, ?int $decimalDigits = null) {
+    parent::__construct($name, $nullable, $defaultValue, $totalDigits, $decimalDigits);
+    $this->type = "DOUBLE";
+  }
+}

Core/Driver/SQL/Column/EnumColumn.class.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class EnumColumn extends Column {
+
+  private array $values;
+
+  public function __construct(string $name, array $values, bool $nullable = false, $defaultValue = NULL) {
+    parent::__construct($name, $nullable, $defaultValue);
+    $this->values = $values;
+  }
+
+  public function addValue(string $value) {
+    $this->values[] = $value;
+  }
+
+  public function getValues(): array { return $this->values; }
+}

Core/Driver/SQL/Column/FloatColumn.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class FloatColumn extends NumericColumn {
+  public function __construct(string $name, bool $nullable, $defaultValue = NULL, ?int $totalDigits = null, ?int $decimalDigits = null) {
+    parent::__construct($name, $nullable, $defaultValue, $totalDigits, $decimalDigits);
+    $this->type = "FLOAT";
+  }
+}

Core/Driver/SQL/Column/IntColumn.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class IntColumn extends Column {
+
+  protected string $type;
+  private bool $unsigned;
+
+  public function __construct(string $name, bool $nullable = false, $defaultValue = NULL, bool $unsigned = false) {
+    parent::__construct($name, $nullable, $defaultValue);
+    $this->type = "INTEGER";
+    $this->unsigned = $unsigned;
+  }
+
+  public function isUnsigned(): bool {
+    return $this->unsigned;
+  }
+
+  public function getType(): string {
+    return $this->type;
+  }
+}

Core/Driver/SQL/Column/JsonColumn.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class JsonColumn extends Column {
+
+  public function __construct(string $name, bool $nullable = false, $defaultValue = null) {
+    parent::__construct($name, $nullable, $defaultValue);
+  }
+
+}

Core/Driver/SQL/Column/NumericColumn.class.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+use Core\Driver\SQL\Column\Column;
+
+class NumericColumn extends Column {
+
+  protected string $type;
+  private ?int $totalDigits;
+  private ?int $decimalDigits;
+
+  public function __construct(string $name, bool $nullable, $defaultValue = NULL, ?int $totalDigits = null, ?int $decimalDigits = null) {
+    parent::__construct($name, $nullable, $defaultValue);
+    $this->totalDigits = $totalDigits;
+    $this->decimalDigits = $decimalDigits;
+    $this->type = "NUMERIC";
+  }
+
+  public function getDecimalDigits(): ?int {
+    return $this->decimalDigits;
+  }
+
+  public function getTotalDigits(): ?int {
+    return $this->totalDigits;
+  }
+
+  public function getTypeName(): string {
+    return $this->type;
+  }
+}

Core/Driver/SQL/Column/SerialColumn.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class SerialColumn extends Column {
+
+  public function __construct(string $name, $defaultValue = NULL) {
+    parent::__construct($name, false, $defaultValue); # not nullable
+  }
+
+}

Core/Driver/SQL/Column/StringColumn.class.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Core\Driver\SQL\Column;
+
+class StringColumn extends Column {
+
+  private ?int $maxSize;
+
+  public function __construct(string $name, ?int $maxSize = null, bool $nullable = false, $defaultValue = null) {
+    parent::__construct($name, $nullable, $defaultValue);
+    $this->maxSize = $maxSize;
+  }
+
+  public function getMaxSize(): ?int { return $this->maxSize; }
+}

Core/Driver/SQL/Condition/Compare.class.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class Compare extends Condition {
+
+  private string $operator;
+  private string $column;
+  private $value;
+
+  public function __construct(string $col, $val, string $operator = '=') {
+    $this->operator = $operator;
+    $this->column = $col;
+    $this->value = $val;
+  }
+
+  public function getColumn(): string { return $this->column; }
+  public function getValue() { return $this->value; }
+  public function getOperator(): string { return $this->operator; }
+
+}

Core/Driver/SQL/Condition/CondAnd.class.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondAnd extends Condition {
+
+  private array $conditions;
+
+  public function __construct(...$conditions) {
+    $this->conditions = $conditions;
+  }
+
+  public function getConditions(): array { return $this->conditions; }
+}

Core/Driver/SQL/Condition/CondBool.class.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondBool extends Condition {
+
+  private $value;
+
+  public function __construct($val) {
+    $this->value = $val;
+  }
+
+  public function getValue() { return $this->value; }
+
+}

Core/Driver/SQL/Condition/CondIn.class.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondIn extends Condition {
+
+  private $needle;
+  private $haystack;
+
+  public function __construct($needle, $haystack) {
+    $this->needle = $needle;
+    $this->haystack = $haystack;
+  }
+
+  public function getNeedle() { return $this->needle; }
+  public function getHaystack() { return $this->haystack; }
+}

Core/Driver/SQL/Condition/CondKeyword.class.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+abstract class CondKeyword extends Condition {
+
+  private $leftExpression;
+  private $rightExpression;
+  private string $keyword;
+
+  public function __construct(string $keyword, $leftExpression, $rightExpression) {
+    $this->leftExpression = $leftExpression;
+    $this->rightExpression = $rightExpression;
+    $this->keyword = $keyword;
+  }
+
+  public function getLeftExp() { return $this->leftExpression; }
+  public function getRightExp() { return $this->rightExpression; }
+  public function getKeyword(): string { return $this->keyword; }
+}

Core/Driver/SQL/Condition/CondLike.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondLike extends CondKeyword {
+
+  public function __construct($leftExpression, $rightExpression) {
+    parent::__construct("LIKE", $leftExpression, $rightExpression);
+  }
+}

Core/Driver/SQL/Condition/CondNot.class.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondNot extends Condition {
+
+  private $expression; // string or condition
+
+  public function __construct($expression) {
+    $this->expression = $expression;
+  }
+
+  public function getExpression() {
+    return $this->expression;
+  }
+}

Core/Driver/SQL/Condition/CondNull.class.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondNull extends Condition {
+
+  private string $column;
+
+  public function __construct(string $col) {
+    $this->column = $col;
+  }
+
+  public function getColumn(): string { return $this->column; }
+}

Core/Driver/SQL/Condition/CondOr.class.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondOr extends Condition {
+
+  private array $conditions;
+
+  public function __construct(...$conditions) {
+    $this->conditions = (!empty($conditions) && is_array($conditions[0])) ? $conditions[0] : $conditions;
+  }
+
+  public function getConditions(): array { return $this->conditions; }
+}

Core/Driver/SQL/Condition/CondRegex.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+class CondRegex extends CondKeyword {
+
+  public function __construct($leftExpression, $rightExpression) {
+    parent::__construct("REGEXP", $leftExpression, $rightExpression);
+  }
+
+}

Core/Driver/SQL/Condition/Condition.class.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace Core\Driver\SQL\Condition;
+
+use Core\Driver\SQL\Expression\Expression;
+
+abstract class Condition extends Expression {
+  
+}

Core/Driver/SQL/Condition/Exists.class.php

@@ -0,0 +1,22 @@
+<?php
+
+
+namespace Core\Driver\SQL\Condition;
+
+
+use Core\Driver\SQL\Query\Select;
+
+class Exists extends Condition
+{
+    private Select $subQuery;
+
+    public function __construct(Select $subQuery)
+    {
+        $this->subQuery = $subQuery;
+    }
+
+    public function getSubQuery(): Select
+    {
+        return $this->subQuery;
+    }
+}

Core/Driver/SQL/Constraint/Constraint.class.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Core\Driver\SQL\Constraint;
+
+abstract class Constraint {
+
+  private array $columnNames;
+  private ?string $name;
+
+  public function __construct($columnNames, ?string $constraintName = NULL) {
+    $this->columnNames = (!is_array($columnNames) ? array($columnNames) : $columnNames);
+    $this->name = $constraintName;
+  }
+
+  public function getColumnNames(): array { return $this->columnNames; }
+  public function getName(): ?string { return $this->name; }
+  public function setName(string $name) { $this->name = $name; }
+}

Core/Driver/SQL/Constraint/ForeignKey.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Core\Driver\SQL\Constraint;
+
+use Core\Driver\SQL\Strategy\Strategy;
+
+class ForeignKey extends Constraint {
+
+  private string $referencedTable;
+  private string $referencedColumn;
+  private ?Strategy $strategy;
+
+  public function __construct(string $columnName, string $refTable, string $refColumn, ?Strategy $strategy = NULL) {
+    parent::__construct($columnName);
+    $this->referencedTable = $refTable;
+    $this->referencedColumn = $refColumn;
+    $this->strategy = $strategy;
+  }
+
+  public function getReferencedTable(): string { return $this->referencedTable; }
+  public function getReferencedColumn(): string { return $this->referencedColumn; }
+  public function onDelete(): ?Strategy { return $this->strategy; }
+}

Core/Driver/SQL/Constraint/PrimaryKey.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Constraint;
+
+class PrimaryKey extends Constraint {
+
+  public function __construct(...$names) {
+    parent::__construct((!empty($names) && is_array($names[0])) ? $names[0] : $names);
+  }
+
+}

Core/Driver/SQL/Constraint/Unique.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Constraint;
+
+class Unique extends Constraint {
+
+  public function __construct(...$names) {
+    parent::__construct((!empty($names) && is_array($names[0])) ? $names[0] : $names);
+  }
+
+}

Core/Driver/SQL/Expression/Add.class.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+use Core\Driver\SQL\Condition\Compare;
+
+# TODO: change confusing class inheritance here
+class Add extends Compare {
+
+  public function __construct(string $col, $val) {
+    parent::__construct($col, $val, "+");
+  }
+
+}

Core/Driver/SQL/Expression/CaseWhen.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+use Core\Driver\SQL\Condition\Condition;
+
+class CaseWhen extends Expression {
+
+  private Condition $condition;
+  private $trueCase;
+  private $falseCase;
+
+  public function __construct(Condition $condition, $trueCase, $falseCase) {
+    $this->condition = $condition;
+    $this->trueCase = $trueCase;
+    $this->falseCase = $falseCase;
+  }
+
+  public function getCondition(): Condition { return $this->condition; }
+  public function getTrueCase() { return $this->trueCase; }
+  public function getFalseCase() { return $this->falseCase; }
+
+}

Core/Driver/SQL/Expression/CurrentTimeStamp.class.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+class CurrentTimeStamp extends Expression {
+
+}

Core/Driver/SQL/Expression/DateAdd.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+use Core\Driver\SQL\SQL;
+
+class DateAdd extends Expression {
+
+  private Expression $lhs;
+  private Expression $rhs;
+  private string $unit;
+
+  public function __construct(Expression $lhs, Expression $rhs, string $unit) {
+    $this->lhs = $lhs;
+    $this->rhs = $rhs;
+    $this->unit = $unit;
+  }
+
+  public function getLHS(): Expression { return $this->lhs; }
+  public function getRHS(): Expression { return $this->rhs; }
+  public function getUnit(): string { return $this->unit; }
+
+}

Core/Driver/SQL/Expression/DateSub.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+use Core\Driver\SQL\SQL;
+
+class DateSub extends Expression {
+
+  private Expression $lhs;
+  private Expression $rhs;
+  private string $unit;
+
+  public function __construct(Expression $lhs, Expression $rhs, string $unit) {
+    $this->lhs = $lhs;
+    $this->rhs = $rhs;
+    $this->unit = $unit;
+  }
+
+  public function getLHS(): Expression { return $this->lhs; }
+  public function getRHS(): Expression { return $this->rhs; }
+  public function getUnit(): string { return $this->unit; }
+
+}

Core/Driver/SQL/Expression/Expression.class.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+use Core\Driver\SQL\SQL;
+
+abstract class Expression {
+
+}

Core/Driver/SQL/Expression/JsonArrayAgg.class.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+class JsonArrayAgg extends Expression {
+
+  private $value;
+  private string $alias;
+
+  public function __construct($value, string $alias) {
+    $this->value = $value;
+    $this->alias = $alias;
+  }
+
+  public function getValue() { return $this->value; }
+  public function getAlias(): string { return $this->alias; }
+
+}

Core/Driver/SQL/Expression/Sum.class.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Core\Driver\SQL\Expression;
+
+class Sum extends Expression {
+
+  private $value;
+  private string $alias;
+
+  public function __construct($value, string $alias) {
+    $this->value = $value;
+    $this->alias = $alias;
+  }
+
+  public function getValue() { return $this->value; }
+  public function getAlias(): string { return $this->alias; }
+
+}

Core/Driver/SQL/Join.class.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Core\Driver\SQL;
+
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\Condition\Compare;
+
+class Join {
+
+  private string $type;
+  private string $table;
+  private string $columnA;
+  private string $columnB;
+  private ?string $tableAlias;
+  private array $conditions;
+
+  public function __construct(string $type, string $table, string $columnA, string $columnB, ?string $tableAlias = null, array $conditions = []) {
+    $this->type = $type;
+    $this->table = $table;
+    $this->columnA = $columnA;
+    $this->columnB = $columnB;
+    $this->tableAlias = $tableAlias;
+    $this->conditions = $conditions;
+    array_unshift($this->conditions , new Compare($columnA, new Column($columnB), "="));
+  }
+
+  public function getType(): string { return $this->type; }
+  public function getTable(): string { return $this->table; }
+  public function getColumnA(): string { return $this->columnA; }
+  public function getColumnB(): string { return $this->columnB; }
+  public function getTableAlias(): ?string { return $this->tableAlias; }
+  public function getConditions(): array { return $this->conditions; }
+
+}

Core/Driver/SQL/Keyword.class.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Core\Driver\SQL;
+
+use Core\Driver\SQL\Expression\Expression;
+
+class Keyword extends Expression {
+
+  private string $value;
+
+  public function __construct(string $value) {
+    $this->value = $value;
+  }
+
+  public function getValue(): string { return $this->value; }
+
+}

Core/Driver/SQL/MySQL.class.php

@@ -0,0 +1,520 @@
+<?php
+
+namespace Core\Driver\SQL;
+
+use Core\API\Parameter\Parameter;
+
+use DateTime;
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\Column\IntColumn;
+use Core\Driver\SQL\Column\NumericColumn;
+use Core\Driver\SQL\Column\SerialColumn;
+use Core\Driver\SQL\Column\StringColumn;
+use Core\Driver\SQL\Column\EnumColumn;
+use Core\Driver\SQL\Column\DateTimeColumn;
+use Core\Driver\SQL\Column\BoolColumn;
+use Core\Driver\SQL\Column\JsonColumn;
+
+use Core\Driver\SQL\Expression\Add;
+use Core\Driver\SQL\Expression\CurrentTimeStamp;
+use Core\Driver\SQL\Expression\DateAdd;
+use Core\Driver\SQL\Expression\DateSub;
+use Core\Driver\SQL\Expression\Expression;
+use Core\Driver\SQL\Expression\JsonArrayAgg;
+use Core\Driver\SQL\Query\CreateProcedure;
+use Core\Driver\SQL\Query\CreateTrigger;
+use Core\Driver\SQL\Query\Query;
+use Core\Driver\SQL\Strategy\Strategy;
+use Core\Driver\SQL\Strategy\UpdateStrategy;
+use Core\Driver\SQL\Type\CurrentColumn;
+use Core\Driver\SQL\Type\CurrentTable;
+use Core\Driver\SQL\Type\Trigger;
+
+class MySQL extends SQL {
+
+  public function __construct($connectionData) {
+    parent::__construct($connectionData);
+  }
+
+  public function checkRequirements() {
+    return function_exists('mysqli_connect');
+  }
+
+  public function getDriverName() {
+    return 'mysqli';
+  }
+
+  // Connection Management
+  public function connect() {
+
+    if (!is_null($this->connection)) {
+      return true;
+    }
+
+    @$this->connection = mysqli_connect(
+      $this->connectionData->getHost(),
+      $this->connectionData->getLogin(),
+      $this->connectionData->getPassword(),
+      $this->connectionData->getProperty('database'),
+      $this->connectionData->getPort()
+    );
+
+    if (mysqli_connect_errno()) {
+      $this->lastError = $this->logger->severe("Failed to connect to MySQL: " . mysqli_connect_error());
+      $this->connection = NULL;
+      return false;
+    }
+
+    mysqli_set_charset($this->connection, $this->connectionData->getProperty('encoding', 'UTF8'));
+    return true;
+  }
+
+  public function disconnect() {
+    if (is_null($this->connection)) {
+      return true;
+    }
+
+    mysqli_close($this->connection);
+    return true;
+  }
+
+  public function getLastError(): string {
+    $lastError = parent::getLastError();
+    if (empty($lastError)) {
+      $lastError = mysqli_error($this->connection);
+    }
+
+    return $lastError;
+  }
+
+  private function getPreparedParams($values): array {
+    $sqlParams = array('');
+    foreach ($values as $value) {
+      $paramType = Parameter::parseType($value);
+      switch ($paramType) {
+        case Parameter::TYPE_BOOLEAN:
+          $value = $value ? 1 : 0;
+          $sqlParams[0] .= 'i';
+          break;
+        case Parameter::TYPE_INT:
+          $sqlParams[0] .= 'i';
+          break;
+        case Parameter::TYPE_FLOAT:
+          $sqlParams[0] .= 'd';
+          break;
+        case Parameter::TYPE_DATE:
+          if ($value instanceof DateTime) {
+            $value = $value->format('Y-m-d');
+          }
+          $sqlParams[0] .= 's';
+          break;
+        case Parameter::TYPE_TIME:
+          if ($value instanceof DateTime) {
+            $value = $value->format('H:i:s');
+          }
+          $sqlParams[0] .= 's';
+          break;
+        case Parameter::TYPE_DATE_TIME:
+          if ($value instanceof DateTime) {
+            $value = $value->format('Y-m-d H:i:s');
+          }
+          $sqlParams[0] .= 's';
+          break;
+        case Parameter::TYPE_ARRAY:
+          $value = json_encode($value);
+          $sqlParams[0] .= 's';
+          break;
+        case Parameter::TYPE_EMAIL:
+        default:
+          $sqlParams[0] .= 's';
+      }
+
+      $sqlParams[] = $value;
+    }
+
+    return $sqlParams;
+  }
+
+  /**
+   * @return mixed
+   */
+  protected function execute($query, $values = NULL, int $fetchType = self::FETCH_NONE) {
+
+    $result = null;
+    $this->lastError = "";
+    $stmt = null;
+    $res = null;
+    $success = false;
+
+    try {
+      if (empty($values)) {
+        $res = mysqli_query($this->connection, $query);
+        $success = ($res !== FALSE);
+        if ($success) {
+          switch ($fetchType) {
+            case self::FETCH_NONE:
+              $result = true;
+              break;
+            case self::FETCH_ONE:
+              $result = $res->fetch_assoc();
+              break;
+            case self::FETCH_ALL:
+              $result = $res->fetch_all(MYSQLI_ASSOC);
+              break;
+            case self::FETCH_ITERATIVE:
+              $result = new RowIteratorMySQL($res);
+              break;
+          }
+        }
+      } else if ($stmt = $this->connection->prepare($query)) {
+
+        $sqlParams = $this->getPreparedParams($values);
+        if ($stmt->bind_param(...$sqlParams)) {
+          if ($stmt->execute()) {
+            if ($fetchType === self::FETCH_NONE) {
+              $result = true;
+              $success = true;
+            } else {
+              $res = $stmt->get_result();
+              if ($res) {
+                switch ($fetchType) {
+                  case self::FETCH_ONE:
+                    $result = $res->fetch_assoc();
+                    break;
+                  case self::FETCH_ALL:
+                    $result = $res->fetch_all(MYSQLI_ASSOC);
+                    break;
+                  case self::FETCH_ITERATIVE:
+                    $result = new RowIteratorMySQL($res);
+                    break;
+                }
+                $success = true;
+              } else {
+                $this->lastError = $this->logger->error("PreparedStatement::get_result failed: $stmt->error ($stmt->errno)");
+              }
+            }
+          } else {
+            $this->lastError = $this->logger->error("PreparedStatement::execute failed: $stmt->error ($stmt->errno)");
+          }
+        } else {
+          $this->lastError = $this->logger->error("PreparedStatement::prepare failed: $stmt->error ($stmt->errno)");
+        }
+      }
+    } catch (\mysqli_sql_exception $exception) {
+      $this->lastError = $this->logger->error("MySQL::execute failed: $stmt->error ($stmt->errno)");
+    } finally {
+
+      if ($res !== null && !is_bool($res) && $fetchType !== self::FETCH_ITERATIVE) {
+        $res->close();
+      }
+
+      if ($stmt !== null && !is_bool($stmt)) {
+        $stmt->close();
+      }
+
+    }
+
+    return $success ? $result : false;
+  }
+
+  public function getOnDuplicateStrategy(?Strategy $strategy, &$params): ?string {
+    if (is_null($strategy)) {
+      return "";
+    } else if ($strategy instanceof UpdateStrategy) {
+      $updateValues = array();
+      foreach ($strategy->getValues() as $key => $value) {
+        $leftColumn = $this->columnName($key);
+        if ($value instanceof Column) {
+          $columnName = $this->columnName($value->getName());
+          $updateValues[] = "$leftColumn=VALUES($columnName)";
+        } else if ($value instanceof Add) {
+          $columnName = $this->columnName($value->getColumn());
+          $operator = $value->getOperator();
+          $value = $value->getValue();
+          $updateValues[] = "$leftColumn=$columnName$operator" . $this->addValue($value, $params);
+        } else {
+          $updateValues[] = "$leftColumn=" . $this->addValue($value, $params);
+        }
+      }
+
+      return " ON DUPLICATE KEY UPDATE " . implode(",", $updateValues);
+    } else {
+      $strategyClass = get_class($strategy);
+      $this->lastError = $this->logger->error("ON DUPLICATE Strategy $strategyClass is not supported yet.");
+      return null;
+    }
+  }
+
+  protected function fetchReturning($res, string $returningCol) {
+    $this->lastInsertId = mysqli_insert_id($this->connection);
+  }
+
+  public function getColumnType(Column $column): ?string {
+    if ($column instanceof StringColumn) {
+      $maxSize = $column->getMaxSize();
+      if ($maxSize) {
+        return "VARCHAR($maxSize)";
+      } else {
+        return "TEXT";
+      }
+    } else if ($column instanceof SerialColumn) {
+      return "INTEGER AUTO_INCREMENT";
+    } else if ($column instanceof IntColumn) {
+      $unsigned = $column->isUnsigned() ? " UNSIGNED" : "";
+      return $column->getType() . $unsigned;
+    } else if ($column instanceof DateTimeColumn) {
+      return "DATETIME";
+    } else if ($column instanceof BoolColumn) {
+      return "BOOLEAN";
+    } else if ($column instanceof JsonColumn) {
+      return "LONGTEXT"; # some maria db setups don't allow JSON here…
+    } else if ($column instanceof NumericColumn) {
+      $digitsTotal = $column->getTotalDigits();
+      $digitsDecimal = $column->getDecimalDigits();
+      $type = $column->getTypeName();
+      if ($digitsTotal !== null) {
+        if ($digitsDecimal !== null) {
+          return "$type($digitsTotal,$digitsDecimal)";
+        } else {
+          return "$type($digitsTotal)";
+        }
+      } else {
+        return $type;
+      }
+    } else {
+      $this->lastError = $this->logger->error("Unsupported Column Type: " . get_class($column));
+      return NULL;
+    }
+  }
+
+  public function getColumnDefinition(Column $column): ?string {
+    $columnName = $this->columnName($column->getName());
+    $defaultValue = $column->getDefaultValue();
+    if ($column instanceof EnumColumn) { // check this, shouldn't it be in getColumnType?
+      $values = array();
+      foreach ($column->getValues() as $value) {
+        $values[] = $this->getValueDefinition($value);
+      }
+
+      $values = implode(",", $values);
+      $type = "ENUM($values)";
+    } else {
+      $type = $this->getColumnType($column);
+      if (!$type) {
+        return null;
+      }
+    }
+
+    if ($type === "LONGTEXT") {
+      $defaultValue = NULL; # must be null :(
+    }
+
+    $notNull = $column->notNull() ? " NOT NULL" : "";
+    if (!is_null($defaultValue) || !$column->notNull()) {
+      $defaultValue = " DEFAULT " . $this->getValueDefinition($defaultValue);
+    } else {
+      $defaultValue = "";
+    }
+
+    return "$columnName $type$notNull$defaultValue";
+  }
+
+  public function getValueDefinition($value) {
+    if (is_numeric($value)) {
+      return $value;
+    } else if (is_bool($value)) {
+      return $value ? "TRUE" : "FALSE";
+    } else if (is_null($value)) {
+      return "NULL";
+    } else if ($value instanceof Keyword) {
+      return $value->getValue();
+    } else if ($value instanceof CurrentTimeStamp) {
+      return "CURRENT_TIMESTAMP";
+    } else {
+      $str = addslashes($value);
+      return "'$str'";
+    }
+  }
+
+  public function addValue($val, &$params = NULL, bool $unsafe = false) {
+    if ($val instanceof Keyword) {
+      return $val->getValue();
+    } else if ($val instanceof CurrentColumn) {
+      return $val->getName();
+    } else if ($val instanceof Column) {
+      return $this->columnName($val->getName());
+    } else if ($val instanceof Expression) {
+      return $this->createExpression($val, $params);
+    } else {
+      if ($unsafe) {
+        return $this->getUnsafeValue($val);
+      } else {
+        $params[] = $val;
+        return "?";
+      }
+    }
+  }
+
+  public function tableName($table): string {
+    if (is_array($table)) {
+      $tables = array();
+      foreach ($table as $t) $tables[] = $this->tableName($t);
+      return implode(",", $tables);
+    } else {
+      $parts = explode(" ", $table);
+      if (count($parts) === 2) {
+        list ($name, $alias) = $parts;
+        return "`$name` $alias";
+      } else {
+        return "`$table`";
+      }
+    }
+  }
+
+  public function columnName($col): string {
+    if ($col instanceof Keyword) {
+      return $col->getValue();
+    } elseif (is_array($col)) {
+      $columns = array();
+      foreach ($col as $c) $columns[] = $this->columnName($c);
+      return implode(",", $columns);
+    } else {
+      if (($index = strrpos($col, ".")) !== FALSE) {
+        $tableName = $this->tableName(substr($col, 0, $index));
+        $columnName = $this->columnName(substr($col, $index + 1));
+        return "$tableName.$columnName";
+      } else if (($index = stripos($col, " as ")) !== FALSE) {
+        $columnName = $this->columnName(trim(substr($col, 0, $index)));
+        $alias = trim(substr($col, $index + 4));
+        return "$columnName as $alias";
+      } else {
+        return "`$col`";
+      }
+    }
+  }
+
+  public function getStatus() {
+    return mysqli_stat($this->connection);
+  }
+
+  public function createTriggerBody(CreateTrigger $trigger, array $parameters = []): ?string {
+    $values = array();
+
+    foreach ($parameters as $paramValue) {
+      if ($paramValue instanceof CurrentTable) {
+        $values[] = $this->getUnsafeValue($trigger->getTable());
+      } elseif ($paramValue instanceof CurrentColumn) {
+        $prefix = ($trigger->getEvent() !== "DELETE" ? "NEW." : "OLD.");
+        $values[] = $this->columnName($prefix . $paramValue->getName());
+      } else {
+        $values[] = $paramValue;
+      }
+    }
+
+    $procName = $trigger->getProcedure()->getName();
+    $procParameters = implode(",", $values);
+    return "CALL $procName($procParameters)";
+  }
+
+  private function getParameterDefinition(Column $parameter, bool $out = false): string {
+    $out = ($out ? "OUT" : "IN");
+    $name = $parameter->getName();
+    $type = $this->getColumnType($parameter);
+    return "$out $name $type";
+  }
+
+  public function getProcedureHead(CreateProcedure $procedure): ?string {
+    $name = $procedure->getName();
+    $returns = $procedure->getReturns();
+    $paramDefs = [];
+
+    foreach ($procedure->getParameters() as $param) {
+      if ($param instanceof Column) {
+        $paramDefs[] = $this->getParameterDefinition($param);
+      } else {
+        $this->lastError = $this->logger->error("PROCEDURE parameter type " . gettype($returns) . "  is not implemented yet");
+        return null;
+      }
+    }
+
+    if ($returns) {
+      if ($returns instanceof Column) {
+        $paramDefs[] = $this->getParameterDefinition($returns, true);
+      } else if (!($returns instanceof Trigger)) { // mysql does not need to return triggers here
+        $this->lastError = $this->logger->error("PROCEDURE RETURN type " . gettype($returns) . "  is not implemented yet");
+        return null;
+      }
+    }
+
+    $paramDefs = implode(",", $paramDefs);
+    return "CREATE PROCEDURE $name($paramDefs)";
+  }
+
+  protected function buildUnsafe(Query $statement): string {
+    $params = [];
+    $query = $statement->build($params);
+
+    foreach ($params as $value) {
+      $query = preg_replace("?", $this->getUnsafeValue($value), $query, 1);
+    }
+
+    return $query;
+  }
+
+  protected function createExpression(Expression $exp, array &$params): ?string {
+    if ($exp instanceof DateAdd || $exp instanceof DateSub) {
+      $lhs = $this->addValue($exp->getLHS(), $params);
+      $rhs = $this->addValue($exp->getRHS(), $params);
+      $unit = $exp->getUnit();
+      $dateFunction = ($exp instanceof DateAdd ? "DATE_ADD" : "DATE_SUB");
+      return "$dateFunction($lhs, INTERVAL $rhs $unit)";
+    } else if ($exp instanceof CurrentTimeStamp) {
+      return "NOW()";
+    } else if ($exp instanceof JsonArrayAgg) {
+      $value = $this->addValue($exp->getValue(), $params);
+      $alias = $this->columnName($exp->getAlias());
+      return "JSON_ARRAYAGG($value) as $alias";
+    } else {
+      return parent::createExpression($exp, $params);
+    }
+  }
+}
+
+class RowIteratorMySQL extends RowIterator {
+
+  public function __construct($resultSet, bool $useCache = false) {
+    parent::__construct($resultSet, $useCache);
+  }
+
+  protected function getNumRows(): int {
+    return $this->resultSet->num_rows;
+  }
+
+  protected function fetchRow(int $index): array {
+    // check if we already fetched that row
+    if (!$this->useCache || $index >= count($this->fetchedRows)) {
+      // if not, fetch it from the result set
+      $row = $this->resultSet->fetch_assoc();
+      if ($this->useCache) {
+        $this->fetchedRows[] = $row;
+      }
+
+      // close result set, after everything's fetched
+      if ($index >= $this->numRows - 1) {
+        $this->resultSet->close();
+      }
+    } else {
+      $row = $this->fetchedRows[$index];
+    }
+
+    return $row;
+  }
+
+  public function rewind() {
+    if ($this->useCache) {
+      $this->rowIndex = 0;
+    } else if ($this->rowIndex !== 0) {
+      throw new \Exception("RowIterator::rewind() not supported, when caching is disabled");
+    }
+  }
+}

Core/Driver/SQL/PostgreSQL.class.php

@@ -0,0 +1,497 @@
+<?php
+
+namespace Core\Driver\SQL;
+
+use Core\API\Parameter\Parameter;
+
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\Column\IntColumn;
+use Core\Driver\SQL\Column\NumericColumn;
+use Core\Driver\SQL\Column\SerialColumn;
+use Core\Driver\SQL\Column\StringColumn;
+use Core\Driver\SQL\Column\EnumColumn;
+use Core\Driver\SQL\Column\DateTimeColumn;
+use Core\Driver\SQL\Column\BoolColumn;
+use Core\Driver\SQL\Column\JsonColumn;
+
+use Core\Driver\SQL\Condition\CondRegex;
+use Core\Driver\SQL\Expression\Add;
+use Core\Driver\SQL\Expression\CurrentTimeStamp;
+use Core\Driver\SQL\Expression\DateAdd;
+use Core\Driver\SQL\Expression\DateSub;
+use Core\Driver\SQL\Expression\Expression;
+use Core\Driver\SQL\Expression\JsonArrayAgg;
+use Core\Driver\SQL\Query\CreateProcedure;
+use Core\Driver\SQL\Query\CreateTrigger;
+use Core\Driver\SQL\Query\Insert;
+use Core\Driver\SQL\Query\Query;
+use Core\Driver\SQL\Strategy\Strategy;
+use Core\Driver\SQL\Strategy\UpdateStrategy;
+use Core\Driver\SQL\Type\CurrentColumn;
+use Core\Driver\SQL\Type\CurrentTable;
+use Core\Driver\SQL\Type\Trigger;
+
+class PostgreSQL extends SQL {
+
+  public function __construct($connectionData) {
+    parent::__construct($connectionData);
+  }
+
+  public function checkRequirements() {
+    return function_exists('pg_connect');
+  }
+
+  public function getDriverName() {
+    return 'pgsql';
+  }
+
+  // Connection Management
+  public function connect() {
+    if (!is_null($this->connection)) {
+      return true;
+    }
+
+    $config = array(
+      "host" => $this->connectionData->getHost(),
+      "port" => $this->connectionData->getPort(),
+      "dbname" => $this->connectionData->getProperty('database', 'public'),
+      "user" => $this->connectionData->getLogin(),
+      "password" => $this->connectionData->getPassword()
+    );
+
+    $connectionString = array();
+    foreach ($config as $key => $val) {
+      if (!empty($val)) {
+        $connectionString[] = "$key=$val";
+      }
+    }
+
+    $this->connection = @pg_connect(implode(" ", $connectionString), PGSQL_CONNECT_FORCE_NEW);
+    if (!$this->connection) {
+      $this->lastError = $this->logger->severe("Failed to connect to Database");
+      $this->connection = NULL;
+      return false;
+    }
+
+    pg_set_client_encoding($this->connection, $this->connectionData->getProperty('encoding', 'UTF-8'));
+    return true;
+  }
+
+  public function disconnect() {
+    if (is_null($this->connection))
+      return;
+
+    @pg_close($this->connection);
+  }
+
+  public function getLastError(): string {
+    $lastError = parent::getLastError();
+    if (empty($lastError)) {
+      $lastError = trim(pg_last_error($this->connection) . " " . pg_last_error($this->connection));
+    }
+
+    return $lastError;
+  }
+
+  /**
+   * @return mixed
+   */
+  protected function execute($query, $values = NULL, int $fetchType = self::FETCH_NONE) {
+
+    $this->lastError = "";
+    $stmt_name = uniqid();
+    $pgParams = array();
+
+    if (!is_null($values)) {
+      foreach ($values as $value) {
+        $paramType = Parameter::parseType($value);
+        switch ($paramType) {
+          case Parameter::TYPE_DATE:
+            $value = $value->format("Y-m-d");
+            break;
+          case Parameter::TYPE_TIME:
+            $value = $value->format("H:i:s");
+            break;
+          case Parameter::TYPE_DATE_TIME:
+            $value = $value->format("Y-m-d H:i:s");
+            break;
+          case Parameter::TYPE_ARRAY:
+            $value = json_encode($value);
+            break;
+          default:
+            break;
+        }
+
+        $pgParams[] = $value;
+      }
+    }
+
+    $stmt = @pg_prepare($this->connection, $stmt_name, $query);
+    if ($stmt === FALSE) {
+      return false;
+    }
+
+    $result = @pg_execute($this->connection, $stmt_name, $pgParams);
+    if ($result === FALSE) {
+      return false;
+    }
+
+    switch ($fetchType) {
+      case self::FETCH_NONE:
+        return true;
+      case self::FETCH_ONE:
+        return pg_fetch_assoc($result);
+      case self::FETCH_ALL:
+        $rows = pg_fetch_all($result);
+        if ($rows === FALSE) {
+          if (empty(trim($this->getLastError()))) {
+            $rows = array();
+          }
+        }
+        return $rows;
+      case self::FETCH_ITERATIVE:
+        return new RowIteratorPostgreSQL($result);
+    }
+  }
+
+  public function getOnDuplicateStrategy(?Strategy $strategy, &$params): ?string {
+    if (!is_null($strategy)) {
+      if ($strategy instanceof UpdateStrategy) {
+        $updateValues = array();
+        foreach ($strategy->getValues() as $key => $value) {
+          $leftColumn = $this->columnName($key);
+          if ($value instanceof Column) {
+            $columnName = $this->columnName($value->getName());
+            $updateValues[] = "$leftColumn=EXCLUDED.$columnName";
+          } else if ($value instanceof Add) {
+            $columnName = $this->columnName($value->getColumn());
+            $operator = $value->getOperator();
+            $value = $value->getValue();
+            $updateValues[] = "$leftColumn=$columnName$operator" . $this->addValue($value, $params);
+          } else {
+            $updateValues[] = "$leftColumn=" . $this->addValue($value, $parameters);
+          }
+        }
+
+        $conflictingColumns = $this->columnName($strategy->getConflictingColumns());
+        $updateValues = implode(",", $updateValues);
+        return " ON CONFLICT ($conflictingColumns) DO UPDATE SET $updateValues";
+      } else {
+        $strategyClass = get_class($strategy);
+        $this->lastError = $this->logger->error("ON DUPLICATE Strategy $strategyClass is not supported yet.");
+        return null;
+      }
+    } else {
+      return "";
+    }
+  }
+
+  public function getReturning(?string $columns): string {
+    return $columns ? (" RETURNING " . $this->columnName($columns)) : "";
+  }
+
+  public function executeQuery(Query $query, int $fetchType = self::FETCH_NONE) {
+
+    if ($query instanceof Insert && !empty($query->getReturning())) {
+      $fetchType = self::FETCH_ONE;
+    }
+
+    return parent::executeQuery($query, $fetchType);
+  }
+
+  protected function fetchReturning($res, string $returningCol) {
+    $this->lastInsertId = $res[0][$returningCol];
+  }
+
+  // UGLY but.. what should i do?
+  private function createEnum(EnumColumn $enumColumn, string $typeName): string {
+    $values = array();
+    foreach ($enumColumn->getValues() as $value) {
+      $values[] = $this->getValueDefinition($value);
+    }
+
+    $values = implode(",", $values);
+    $query =
+      "DO $$ BEGIN
+        CREATE TYPE \"$typeName\" AS ENUM ($values);
+      EXCEPTION
+        WHEN duplicate_object THEN null;
+      END $$;";
+
+    return $this->execute($query);
+  }
+
+  public function getColumnType(Column $column): ?string {
+    if ($column instanceof StringColumn) {
+      $maxSize = $column->getMaxSize();
+      if ($maxSize) {
+        return "VARCHAR($maxSize)";
+      } else {
+        return "TEXT";
+      }
+    } else if ($column instanceof SerialColumn) {
+      return "SERIAL";
+    } else if ($column instanceof IntColumn) {
+      return $column->getType();
+    } else if ($column instanceof DateTimeColumn) {
+      return "TIMESTAMP";
+    } else if ($column instanceof EnumColumn) {
+      $typeName = $column->getName();
+      if (!endsWith($typeName, "_type")) {
+        $typeName = "${typeName}_type";
+      }
+      return $typeName;
+    } else if ($column instanceof BoolColumn) {
+      return "BOOLEAN";
+    } else if ($column instanceof JsonColumn) {
+      return "JSON";
+    } else if ($column instanceof NumericColumn) {
+      $digitsDecimal = $column->getDecimalDigits();
+      $type = $column->getTypeName();
+      if ($digitsDecimal !== null) {
+        if ($type === "double") {
+          $type = "float"; // postgres doesn't know about double :/
+        }
+        return "$type($digitsDecimal)";
+      } else {
+        return $type;
+      }
+    } else {
+      $this->lastError = $this->logger->error("Unsupported Column Type: " . get_class($column));
+      return NULL;
+    }
+  }
+
+  public function getColumnDefinition($column): ?string {
+    $columnName = $this->columnName($column->getName());
+
+    $type = $this->getColumnType($column);
+    if (!$type) {
+      return null;
+    } else if ($column instanceof EnumColumn) {
+      if (!$this->createEnum($column, $type)) {
+        return null;
+      }
+    }
+
+    $notNull = $column->notNull() ? " NOT NULL" : "";
+    $defaultValue = "";
+    if (!is_null($column->getDefaultValue()) || !$column->notNull()) {
+      $defaultValue = " DEFAULT " . $this->getValueDefinition($column->getDefaultValue());
+    }
+
+    return "$columnName $type$notNull$defaultValue";
+  }
+
+  protected function getValueDefinition($value) {
+    if (is_numeric($value)) {
+      return $value;
+    } else if (is_bool($value)) {
+      return $value ? "TRUE" : "FALSE";
+    } else if (is_null($value)) {
+      return "NULL";
+    } else if ($value instanceof Keyword) {
+      return $value->getValue();
+    } else if ($value instanceof CurrentTimeStamp) {
+      return "CURRENT_TIMESTAMP";
+    } else {
+      $str = str_replace("'", "''", $value);
+      return "'$str'";
+    }
+  }
+
+  public function addValue($val, &$params = NULL, bool $unsafe = false) {
+    if ($val instanceof Keyword) {
+      return $val->getValue();
+    } else if ($val instanceof CurrentTable) {
+      return "TG_TABLE_NAME";
+    } else if ($val instanceof CurrentColumn) {
+      return "NEW." . $this->columnName($val->getName());
+    } else if ($val instanceof Column) {
+      return $this->columnName($val->getName());
+    } else if ($val instanceof Expression) {
+      return $this->createExpression($val, $params);
+    } else {
+      if ($unsafe) {
+        return $this->getUnsafeValue($val);
+      } else {
+        $params[] = is_bool($val) ? ($val ? "TRUE" : "FALSE") : $val;
+        return '$' . count($params);
+      }
+    }
+  }
+
+  public function tableName($table): string {
+    if (is_array($table)) {
+      $tables = array();
+      foreach ($table as $t) $tables[] = $this->tableName($t);
+      return implode(",", $tables);
+    } else {
+      $parts = explode(" ", $table);
+      if (count($parts) === 2) {
+        list ($name, $alias) = $parts;
+        return "\"$name\" $alias";
+      } else {
+        return "\"$table\"";
+      }
+    }
+  }
+
+  public function columnName($col): string {
+    if ($col instanceof KeyWord) {
+      return $col->getValue();
+    } elseif (is_array($col)) {
+      $columns = array_map(function ($c) {
+        return $this->columnName($c);
+      }, $col);
+      return implode(",", $columns);
+    } else {
+      if (($index = strrpos($col, ".")) !== FALSE) {
+        $tableName = $this->tableName(substr($col, 0, $index));
+        $columnName = $this->columnName(substr($col, $index + 1));
+        return "$tableName.$columnName";
+      } else if (($index = stripos($col, " as ")) !== FALSE) {
+        $columnName = $this->columnName(trim(substr($col, 0, $index)));
+        $alias = $this->columnName(trim(substr($col, $index + 4)));
+        return "$columnName as $alias";
+      } else {
+        return "\"$col\"";
+      }
+    }
+  }
+
+  public function getStatus() {
+    $version = pg_version($this->connection)["client"] ?? "??";
+    $status = pg_connection_status($this->connection);
+    static $statusTexts = array(
+      PGSQL_CONNECTION_OK => "PGSQL_CONNECTION_OK",
+      PGSQL_CONNECTION_BAD => "PGSQL_CONNECTION_BAD",
+    );
+
+    return ($statusTexts[$status] ?? "Unknown") . " (v$version)";
+  }
+
+  public function buildCondition($condition, &$params) {
+    if ($condition instanceof CondRegex) {
+      $left = $condition->getLeftExp();
+      $right = $condition->getRightExp();
+      $left = ($left instanceof Column) ? $this->columnName($left->getName()) : $this->addValue($left, $params);
+      $right = ($right instanceof Column) ? $this->columnName($right->getName()) : $this->addValue($right, $params);
+      return $left . " ~ " . $right;
+    } else {
+      return parent::buildCondition($condition, $params);
+    }
+  }
+
+  private function createTriggerProcedure(string $name, array $statements) {
+    $params = [];
+    $query = "CREATE OR REPLACE FUNCTION $name() RETURNS TRIGGER AS \$table\$ BEGIN ";
+    foreach ($statements as $stmt) {
+      if ($stmt instanceof Keyword) {
+        $query .= $stmt->getValue() . ";";
+      } else {
+        $query .= $stmt->build($this, $params) . ";";
+      }
+    }
+    $query .= "END;";
+    $query .= "\$table\$ LANGUAGE plpgsql;";
+
+    return $this->execute($query, $params);
+  }
+
+  public function createTriggerBody(CreateTrigger $trigger, array $params = []): ?string {
+    $procName = $this->tableName($trigger->getProcedure()->getName());
+    return "EXECUTE PROCEDURE $procName()";
+  }
+
+  public function getProcedureHead(CreateProcedure $procedure): ?string {
+    $name = $this->tableName($procedure->getName());
+    $returns = $procedure->getReturns() ?? "";
+    $paramDefs = [];
+
+    if (!($procedure->getReturns() instanceof Trigger)) {
+      foreach ($procedure->getParameters() as $parameter) {
+        $paramDefs[] = $parameter->getName() . " " . $this->getColumnType($parameter);
+      }
+    }
+
+    $paramDefs = implode(",", $paramDefs);
+    if ($returns) {
+      if ($returns instanceof Column) {
+        $returns = " RETURNS " . $this->getColumnType($returns);
+      } else if ($returns instanceof Keyword) {
+        $returns = " RETURNS " . $returns->getValue();
+      }
+    }
+
+    return "CREATE OR REPLACE FUNCTION $name($paramDefs)$returns AS $$";
+  }
+
+  public function getProcedureTail(): string {
+    return "$$ LANGUAGE plpgsql;";
+  }
+
+  public function getProcedureBody(CreateProcedure $procedure): string {
+    $statements = parent::getProcedureBody($procedure);
+    if ($procedure->getReturns() instanceof Trigger) {
+      $statements .= "RETURN NEW;";
+    }
+    return $statements;
+  }
+
+  protected function buildUnsafe(Query $statement): string {
+    $params = [];
+    $query = $statement->build($params);
+
+    foreach ($params as $index => $value) {
+      $value = $this->getUnsafeValue($value);
+      $query = preg_replace("\$$index", $value, $query, 1);
+    }
+
+    return $query;
+  }
+
+  protected function createExpression(Expression $exp, array &$params): ?string {
+    if ($exp instanceof DateAdd || $exp instanceof DateSub) {
+      $lhs = $this->addValue($exp->getLHS(), $params);
+      $rhs = $this->addValue($exp->getRHS(), $params);
+      $unit = $exp->getUnit();
+
+      if ($exp->getRHS() instanceof Column) {
+        $rhs = "$rhs * INTERVAL '1 $unit'";
+      } else {
+        $rhs = "$rhs $unit";
+      }
+
+      $operator = ($exp instanceof DateAdd ? "+" : "-");
+      return "$lhs $operator $rhs";
+    } else if ($exp instanceof CurrentTimeStamp) {
+      return "CURRENT_TIMESTAMP";
+    } else if ($exp instanceof JsonArrayAgg) {
+      $value = $this->addValue($exp->getValue(), $params);
+      $alias = $this->columnName($exp->getAlias());
+      return "JSON_AGG($value) as $alias";
+    } else {
+      return parent::createExpression($exp, $params);
+    }
+  }
+}
+
+class RowIteratorPostgreSQL extends RowIterator {
+
+  public function __construct($resultSet, bool $useCache = false) {
+    parent::__construct($resultSet, false);  // caching not needed
+  }
+
+  protected function getNumRows(): int {
+    return pg_num_rows($this->resultSet);
+  }
+
+  public function rewind() {
+    $this->rowIndex = 0;
+  }
+
+  protected function fetchRow(int $index): array {
+    return pg_fetch_assoc($this->resultSet, $index);
+  }
+}

Core/Driver/SQL/Query/AlterTable.class.php

@@ -0,0 +1,133 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\Column\EnumColumn;
+use Core\Driver\SQL\Constraint\Constraint;
+use Core\Driver\SQL\Constraint\ForeignKey;
+use Core\Driver\SQL\Constraint\PrimaryKey;
+use Core\Driver\SQL\PostgreSQL;
+use Core\Driver\SQL\SQL;
+
+class AlterTable extends Query {
+
+  private string $table;
+  private string $action;
+  private $data;
+
+  private ?Column $column;
+  private ?Constraint $constraint;
+
+  public function __construct(SQL $sql, string $table) {
+    parent::__construct($sql);
+    $this->table = $table;
+    $this->column = null;
+    $this->constraint = null;
+  }
+
+  public function add($what): AlterTable {
+    if ($what instanceof Column) {
+      $this->column = $what;
+    } else if ($what instanceof Constraint) {
+      $this->constraint = $what;
+    } else {
+      $this->column = new Column($what);
+    }
+
+    $this->action = "ADD";
+    return $this;
+  }
+
+  public function modify(Column $column): AlterTable {
+    $this->column = $column;
+    $this->action = "MODIFY";
+    return $this;
+  }
+
+  public function drop($what): AlterTable {
+    if ($what instanceof Column) {
+      $this->column = $what;
+    } else if ($what instanceof Constraint) {
+      $this->constraint = $what;
+    } else {
+      $this->column = new Column($what);
+    }
+    $this->action = "DROP";
+    return $this;
+  }
+
+  public function resetAutoIncrement(): AlterTable {
+    $this->action = "RESET_AUTO_INCREMENT";
+    return $this;
+  }
+
+  public function addToEnum(EnumColumn $column, string $newValue): AlterTable {
+    $this->action = "MODIFY";
+    $this->column = $column;
+    $this->data = $newValue;
+    return $this;
+  }
+
+  public function getAction(): string { return $this->action; }
+  public function getColumn(): ?Column { return $this->column; }
+  public function getConstraint(): ?Constraint { return $this->constraint; }
+  public function getTable(): string { return $this->table; }
+
+  public function build(array &$params): ?string {
+    $tableName = $this->sql->tableName($this->getTable());
+    $action = $this->getAction();
+    $column = $this->getColumn();
+    $constraint = $this->getConstraint();
+
+    if ($action === "RESET_AUTO_INCREMENT") {
+      return "ALTER TABLE $tableName AUTO_INCREMENT=1";
+    }
+
+    $query = "ALTER TABLE $tableName $action ";
+
+    if ($column) {
+      $query .= "COLUMN ";
+      if ($action === "DROP") {
+        $query .= $this->sql->columnName($column->getName());
+      } else {
+        // ADD or modify
+        if ($column instanceof EnumColumn) {
+          if ($this->sql instanceof PostgreSQL) {
+            $typeName = $this->sql->getColumnType($column);
+            $value = $this->sql->addValue($this->data, $params);
+            return "ALTER TYPE $typeName ADD VALUE $value";
+          }
+          $column->addValue($this->data);
+        }
+
+        $query .= $this->sql->getColumnDefinition($column);
+      }
+    } else if ($constraint) {
+      if ($action === "DROP") {
+        if ($constraint instanceof PrimaryKey) {
+          $query .= "PRIMARY KEY";
+        } else {
+          $constraintName = $constraint->getName();
+          if ($constraintName) {
+            $query .= "CONSTRAINT " . $this->sql->columnName($constraintName);
+          } else {
+            $this->sql->setLastError("Cannot DROP CONSTRAINT without a constraint name.");
+            return null;
+          }
+        }
+      } else if ($action === "ADD") {
+        $query .= "CONSTRAINT ";
+        $query .= $this->sql->getConstraintDefinition($constraint);
+      } else if ($action === "MODIFY") {
+        $this->sql->setLastError("MODIFY CONSTRAINT foreign key is not supported.");
+        return null;
+      }
+    } else {
+      $this->sql->setLastError("'ALTER TABLE' requires at least a column or a constraint.");
+      return null;
+    }
+
+    return $query;
+  }
+}

Core/Driver/SQL/Query/Commit.class.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\SQL;
+
+class Commit extends Query {
+  public function __construct(SQL $sql) {
+    parent::__construct($sql);
+  }
+
+  public function build(array &$params): ?string {
+    return "COMMIT";
+  }
+}

Core/Driver/SQL/Query/CreateProcedure.class.php

@@ -0,0 +1,50 @@
+<?php
+
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\SQL;
+
+class CreateProcedure extends Query {
+
+  private string $name;
+  private array $parameters;
+  private array $statements;
+  private $returns;
+
+  public function __construct(SQL $sql, string $procName) {
+    parent::__construct($sql);
+    $this->name = $procName;
+    $this->parameters = [];
+    $this->statements = [];
+    $this->returns = NULL;
+  }
+
+  public function param(Column $parameter): CreateProcedure {
+    $this->parameters[] = $parameter;
+    return $this;
+  }
+
+  public function returns($column): CreateProcedure {
+    $this->returns = $column;
+    return $this;
+  }
+
+  public function exec(array $statements): CreateProcedure {
+    $this->statements = $statements;
+    return $this;
+  }
+
+  public function build(array &$params): ?string {
+    $head = $this->sql->getProcedureHead($this);
+    $body = $this->sql->getProcedureBody($this);
+    $tail = $this->sql->getProcedureTail();
+    return "$head BEGIN $body END; $tail";
+  }
+
+  public function getName(): string { return $this->name; }
+  public function getParameters(): array { return $this->parameters; }
+  public function getReturns() { return $this->returns; }
+  public function getStatements(): array { return $this->statements; }
+}

Core/Driver/SQL/Query/CreateTable.class.php

@@ -0,0 +1,156 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Column\BigIntColumn;
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\Column\DoubleColumn;
+use Core\Driver\SQL\Column\FloatColumn;
+use Core\Driver\SQL\Column\NumericColumn;
+use Core\Driver\SQL\Column\SerialColumn;
+use Core\Driver\SQL\Column\StringColumn;
+use Core\Driver\SQL\Column\IntColumn;
+use Core\Driver\SQL\Column\DateTimeColumn;
+use Core\Driver\SQL\Column\EnumColumn;
+use Core\Driver\SQL\Column\BoolColumn;
+use Core\Driver\SQL\Column\JsonColumn;
+
+use Core\Driver\SQL\Constraint\Constraint;
+use Core\Driver\SQL\Constraint\PrimaryKey;
+use Core\Driver\SQL\Constraint\Unique;
+use Core\Driver\SQL\Constraint\ForeignKey;
+use Core\Driver\SQL\SQL;
+use Core\Driver\SQL\Strategy\Strategy;
+
+class CreateTable extends Query {
+
+  private string $tableName;
+  private array $columns;
+  private array $constraints;
+  private bool $ifNotExists;
+
+  public function __construct(SQL $sql, string $name) {
+    parent::__construct($sql);
+    $this->tableName = $name;
+    $this->columns = array();
+    $this->constraints = array();
+    $this->ifNotExists = false;
+  }
+
+  public function addColumn(Column $column): CreateTable {
+    $this->columns[$column->getName()] = $column;
+    return $this;
+  }
+
+  public function addConstraint(Constraint $constraint): CreateTable {
+    $this->constraints[] = $constraint;
+    return $this;
+  }
+
+  public function addSerial(string $name): CreateTable {
+    $this->columns[$name] = new SerialColumn($name);
+    return $this;
+  }
+
+  public function addString(string $name, ?int $maxSize = NULL, bool $nullable = false, $defaultValue = NULL): CreateTable {
+    $this->columns[$name] = new StringColumn($name, $maxSize, $nullable, $defaultValue);
+    return $this;
+  }
+
+  public function addDateTime(string $name, bool $nullable = false, $defaultValue = NULL): CreateTable {
+    $this->columns[$name] = new DateTimeColumn($name, $nullable, $defaultValue);
+    return $this;
+  }
+
+  public function addInt(string $name, bool $nullable = false, $defaultValue = NULL, bool $unsigned = false): CreateTable {
+    $this->columns[$name] = new IntColumn($name, $nullable, $defaultValue, $unsigned);
+    return $this;
+  }
+
+  public function addBigInt(string $name, bool $nullable = false, $defaultValue = NULL, bool $unsigned = false): CreateTable {
+    $this->columns[$name] = new BigIntColumn($name, $nullable, $defaultValue, $unsigned);
+    return $this;
+  }
+
+  public function addBool(string $name, $defaultValue = false): CreateTable {
+    $this->columns[$name] = new BoolColumn($name, $defaultValue);
+    return $this;
+  }
+
+  public function addJson(string $name, bool $nullable = false, $defaultValue = NULL): CreateTable {
+    $this->columns[$name] = new JsonColumn($name, $nullable, $defaultValue);
+    return $this;
+  }
+
+  public function addEnum(string $name, array $values, bool $nullable = false, $defaultValue = NULL): CreateTable {
+    $this->columns[$name] = new EnumColumn($name, $values, $nullable, $defaultValue);
+    return $this;
+  }
+
+  public function addNumeric(string $name, bool $nullable = false, $defaultValue = NULL, ?int $digitsTotal = 10, ?int $digitsDecimal = 0): CreateTable {
+    $this->columns[$name] = new NumericColumn($name, $nullable, $defaultValue, $digitsTotal, $digitsDecimal);
+    return $this;
+  }
+
+  public function addFloat(string $name, bool $nullable = false, $defaultValue = NULL, ?int $digitsTotal = null, ?int $digitsDecimal = null): CreateTable {
+    $this->columns[$name] = new FloatColumn($name, $nullable, $defaultValue, $digitsTotal, $digitsDecimal);
+    return $this;
+  }
+
+  public function addDouble(string $name, bool $nullable = false, $defaultValue = NULL, ?int $digitsTotal = null, ?int $digitsDecimal = null): CreateTable {
+    $this->columns[$name] = new DoubleColumn($name, $nullable, $defaultValue, $digitsTotal, $digitsDecimal);
+    return $this;
+  }
+
+  public function primaryKey(...$names): CreateTable {
+    $pk = new PrimaryKey($names);
+    $pk->setName(strtolower("pk_{$this->tableName}"));
+    $this->constraints[] = $pk;
+    return $this;
+  }
+
+  public function unique(...$names): CreateTable {
+    $this->constraints[] = new Unique($names);
+    return $this;
+  }
+
+  public function foreignKey(string $column, string $refTable, string $refColumn, ?Strategy $strategy = NULL): CreateTable {
+    $fk = new ForeignKey($column, $refTable, $refColumn, $strategy);
+    $fk->setName(strtolower("fk_{$this->tableName}_${refTable}_${refColumn}"));
+    $this->constraints[] = $fk;
+    return $this;
+  }
+
+  public function onlyIfNotExists(): CreateTable {
+    $this->ifNotExists = true;
+    return $this;
+  }
+
+  public function ifNotExists(): bool { return $this->ifNotExists; }
+  public function getTableName(): string { return $this->tableName; }
+  public function getColumns(): array { return $this->columns; }
+  public function getConstraints(): array { return $this->constraints; }
+
+  public function build(array &$params): ?string {
+    $tableName = $this->sql->tableName($this->getTableName());
+    $ifNotExists = $this->ifNotExists() ? " IF NOT EXISTS" : "";
+
+    $entries = array();
+    foreach ($this->getColumns() as $column) {
+      $entries[] = ($tmp = $this->sql->getColumnDefinition($column));
+      if (is_null($tmp)) {
+        return false;
+      }
+    }
+
+    foreach ($this->getConstraints() as $constraint) {
+      $entries[] = ($tmp = $this->sql->getConstraintDefinition($constraint));
+      if (is_null($tmp)) {
+        return false;
+      }
+    }
+
+    $entries = implode(",", $entries);
+    return "CREATE TABLE$ifNotExists $tableName ($entries)";
+  }
+}

Core/Driver/SQL/Query/CreateTrigger.class.php

@@ -0,0 +1,83 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\API\User\Create;
+use Core\Driver\SQL\SQL;
+
+class CreateTrigger extends Query {
+
+  private string $name;
+  private string $time;
+  private string $event;
+  private string $tableName;
+  private array $parameters;
+  private ?CreateProcedure $procedure;
+
+  public function __construct(SQL $sql, string $triggerName) {
+    parent::__construct($sql);
+    $this->name = $triggerName;
+    $this->time = "AFTER";
+    $this->tableName = "";
+    $this->event = "";
+    $this->parameters = [];
+    $this->procedure = null;
+  }
+
+  public function before(): CreateTrigger {
+    $this->time = "BEFORE";
+    return $this;
+  }
+
+  public function after(): CreateTrigger {
+    $this->time = "AFTER";
+    return $this;
+  }
+
+  public function update(string $table): CreateTrigger {
+    $this->tableName = $table;
+    $this->event = "UPDATE";
+    return $this;
+  }
+
+  public function insert(string $table): CreateTrigger {
+    $this->tableName = $table;
+    $this->event = "INSERT";
+    return $this;
+  }
+
+  public function delete(string $table): CreateTrigger {
+    $this->tableName = $table;
+    $this->event = "DELETE";
+    return $this;
+  }
+
+  public function exec(CreateProcedure $procedure, array $parameters = []): CreateTrigger {
+    $this->procedure = $procedure;
+    $this->parameters = $parameters;
+    return $this;
+  }
+
+  public function getName(): string { return $this->name; }
+  public function getTime(): string { return $this->time; }
+  public function getEvent(): string { return $this->event; }
+  public function getTable(): string { return $this->tableName; }
+  public function getProcedure(): CreateProcedure { return $this->procedure; }
+
+  public function build(array &$params): ?string {
+    $name = $this->sql->tableName($this->getName());
+    $time = $this->getTime();
+    $event = $this->getEvent();
+    $tableName = $this->sql->tableName($this->getTable());
+
+    $params = array();
+    $query = "CREATE TRIGGER $name $time $event ON $tableName FOR EACH ROW ";
+    $triggerBody = $this->sql->createTriggerBody($this, $this->parameters);
+    if ($triggerBody === null) {
+      return null;
+    }
+
+    $query .= $triggerBody;
+    return $query;
+  }
+}

Core/Driver/SQL/Query/Delete.class.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Condition\CondOr;
+use Core\Driver\SQL\SQL;
+
+class Delete extends Query {
+
+  private string $table;
+  private array $conditions;
+
+  public function __construct(SQL $sql, string $table) {
+    parent::__construct($sql);
+    $this->table = $table;
+    $this->conditions = array();
+  }
+
+  public function where(...$conditions): Delete {
+    $this->conditions[] = (count($conditions) === 1 ? $conditions : new CondOr($conditions));
+    return $this;
+  }
+
+  public function getTable(): string { return $this->table; }
+  public function getConditions(): array { return $this->conditions; }
+
+  public function build(array &$params): ?string {
+    $table = $this->sql->tableName($this->getTable());
+    $where = $this->sql->getWhereClause($this->getConditions(), $params);
+    return "DELETE FROM $table$where";
+  }
+}

Core/Driver/SQL/Query/Drop.php

@@ -0,0 +1,29 @@
+<?php
+
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\SQL;
+
+class Drop extends Query {
+
+  private string $table;
+
+  /**
+   * Drop constructor.
+   * @param SQL $sql
+   * @param string $table
+   */
+  public function __construct(SQL $sql, string $table) {
+    parent::__construct($sql);
+    $this->table = $table;
+  }
+
+  public function getTable(): string {
+    return $this->table;
+  }
+
+  public function build(array &$params): ?string {
+    return "DROP TABLE " . $this->sql->tableName($this->getTable());
+  }
+}

Core/Driver/SQL/Query/Insert.class.php

@@ -0,0 +1,83 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\SQL;
+use Core\Driver\SQL\Strategy\Strategy;
+
+class Insert extends Query {
+
+  private string $tableName;
+  private array $columns;
+  private array $rows;
+  private ?Strategy $onDuplicateKey;
+  private ?string $returning;
+
+  public function __construct(SQL $sql, string $name, array $columns = array()) {
+    parent::__construct($sql);
+    $this->tableName = $name;
+    $this->columns = $columns;
+    $this->rows = array();
+    $this->onDuplicateKey = NULL;
+    $this->returning = NULL;
+  }
+
+  public function addRow(...$values): Insert {
+    $this->rows[] = $values;
+    return $this;
+  }
+
+  public function onDuplicateKeyStrategy(Strategy $strategy): Insert {
+    $this->onDuplicateKey = $strategy;
+    return $this;
+  }
+
+  public function returning(string $column): Insert {
+    $this->returning = $column;
+    return $this;
+  }
+
+  public function getTableName(): string { return $this->tableName; }
+  public function getColumns(): array { return $this->columns; }
+  public function getRows(): array { return $this->rows; }
+  public function onDuplicateKey(): ?Strategy { return $this->onDuplicateKey; }
+  public function getReturning(): ?string { return $this->returning; }
+
+  public function build(array &$params): ?string {
+    $tableName = $this->sql->tableName($this->getTableName());
+    $columns = $this->getColumns();
+    $rows = $this->getRows();
+
+    if (empty($rows)) {
+      $this->sql->setLastError("No rows to insert given.");
+      return null;
+    }
+
+    if (is_null($columns) || empty($columns)) {
+      $columnStr = "";
+    } else {
+      $columnStr = " (" . $this->sql->columnName($columns) . ")";
+    }
+
+    $values = array();
+    foreach ($rows as $row) {
+      $rowPlaceHolder = array();
+      foreach ($row as $val) {
+        $rowPlaceHolder[] = $this->sql->addValue($val, $params);
+      }
+
+      $values[] = "(" . implode(",", $rowPlaceHolder) . ")";
+    }
+
+    $values = implode(",", $values);
+
+    $onDuplicateKey = $this->sql->getOnDuplicateStrategy($this->onDuplicateKey(), $params);
+    if ($onDuplicateKey === FALSE) {
+      return null;
+    }
+
+    $returningCol = $this->getReturning();
+    $returning = $this->sql->getReturning($returningCol);
+    return "INSERT INTO $tableName$columnStr VALUES $values$onDuplicateKey$returning";
+  }
+}

Core/Driver/SQL/Query/Query.class.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Expression\Expression;
+use Core\Driver\SQL\SQL;
+
+abstract class Query extends Expression {
+
+  protected SQL $sql;
+  public bool $dump;
+
+  public function __construct(SQL $sql) {
+    $this->sql = $sql;
+    $this->dump = false;
+  }
+
+  public function dump(): Query {
+    $this->dump = true;
+    return $this;
+  }
+
+  // can actually return bool|array (depending on success and query type)
+  public function execute() {
+    return $this->sql->executeQuery($this);
+  }
+
+  public abstract function build(array &$params): ?string;
+}

Core/Driver/SQL/Query/RollBack.class.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\SQL;
+
+class RollBack extends Query {
+  public function __construct(SQL $sql) {
+    parent::__construct($sql);
+  }
+
+  public function build(array &$params): ?string {
+    return "ROLLBACK";
+  }
+}

Core/Driver/SQL/Query/Select.class.php

@@ -0,0 +1,214 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Condition\CondOr;
+use Core\Driver\SQL\Expression\JsonArrayAgg;
+use Core\Driver\SQL\Join;
+use Core\Driver\SQL\SQL;
+
+class Select extends Query {
+
+  private array $selectValues;
+  private array $tables;
+  private array $conditions;
+  private array $joins;
+  private array $orderColumns;
+  private array $groupColumns;
+  private array $havings;
+  private bool $sortAscending;
+  private int $limit;
+  private int $offset;
+  private bool $forUpdate;
+  private int $fetchType;
+
+  public function __construct($sql, ...$selectValues) {
+    parent::__construct($sql);
+    $this->selectValues = (!empty($selectValues) && is_array($selectValues[0])) ? $selectValues[0] : $selectValues;
+    $this->tables = array();
+    $this->conditions = array();
+    $this->havings = array();
+    $this->joins = array();
+    $this->orderColumns = array();
+    $this->groupColumns = array();
+    $this->limit = 0;
+    $this->offset = 0;
+    $this->sortAscending = true;
+    $this->forUpdate = false;
+    $this->fetchType = SQL::FETCH_ALL;
+  }
+
+  public function from(...$tables): Select {
+    $this->tables = array_merge($this->tables, $tables);
+    return $this;
+  }
+
+  public function addValue($value): Select {
+    $this->selectValues[] = $value;
+    return $this;
+  }
+
+  public function where(...$conditions): Select {
+    $this->conditions[] = (count($conditions) === 1 ? $conditions : new CondOr($conditions));
+    return $this;
+  }
+
+  public function having(...$conditions): Select {
+    $this->havings[] = (count($conditions) === 1 ? $conditions : new CondOr($conditions));
+    return $this;
+  }
+
+  public function innerJoin(string $table, string $columnA, string $columnB, ?string $tableAlias = null, array $conditions = []): Select {
+    $this->joins[] = new Join("INNER", $table, $columnA, $columnB, $tableAlias, $conditions);
+    return $this;
+  }
+
+  public function leftJoin(string $table, string $columnA, string $columnB, ?string $tableAlias = null, array $conditions = []): Select {
+    $this->joins[] = new Join("LEFT", $table, $columnA, $columnB, $tableAlias, $conditions);
+    return $this;
+  }
+
+  public function addJoin(Join $join): Select {
+    $this->joins[] = $join;
+    return $this;
+  }
+
+  public function groupBy(...$columns): Select {
+    $this->groupColumns = $columns;
+    return $this;
+  }
+
+  public function orderBy(...$columns): Select {
+    $this->orderColumns = $columns;
+    return $this;
+  }
+
+  public function ascending(): Select {
+    $this->sortAscending = true;
+    return $this;
+  }
+
+  public function descending(): Select {
+    $this->sortAscending = false;
+    return $this;
+  }
+
+  public function limit(int $limit): Select {
+    $this->limit = $limit;
+    return $this;
+  }
+
+  public function offset(int $offset): Select {
+    $this->offset = $offset;
+    return $this;
+  }
+
+  public function lockForUpdate(): Select {
+    $this->forUpdate = true;
+    return $this;
+  }
+
+  public function iterator(): Select {
+    $this->fetchType = SQL::FETCH_ITERATIVE;
+    return $this;
+  }
+
+  public function first(): Select {
+    $this->fetchType = SQL::FETCH_ONE;
+    $this->limit = 1;
+    return $this;
+  }
+
+  /**
+   * @return mixed
+   */
+  public function execute() {
+    return $this->sql->executeQuery($this, $this->fetchType);
+  }
+
+  public function getSelectValues(): array { return $this->selectValues; }
+  public function getTables(): array { return $this->tables; }
+  public function getConditions(): array { return $this->conditions; }
+  public function getJoins(): array { return $this->joins; }
+  public function isOrderedAscending(): bool { return $this->sortAscending; }
+  public function getOrderBy(): array { return $this->orderColumns; }
+  public function getLimit(): int { return $this->limit; }
+  public function getOffset(): int { return $this->offset; }
+  public function getGroupBy(): array { return $this->groupColumns; }
+  public function getHavings(): array { return $this->havings; }
+
+  public function build(array &$params): ?string {
+
+    $selectValues = [];
+    foreach ($this->selectValues as $value) {
+      if (is_string($value)) {
+        $selectValues[] = $this->sql->columnName($value);
+      } else if ($value instanceof Select) {
+        $subSelect = $value->build($params);
+        if (count($value->getSelectValues()) !== 1) {
+          $selectValues[] = "($subSelect)";
+        } else {
+          $columnAlias = null;
+          $subSelectColumn = $value->getSelectValues()[0];
+          if (is_string($subSelectColumn) && ($index = stripos($subSelectColumn, " as ")) !== FALSE) {
+            $columnAlias = substr($subSelectColumn, $index + 4);
+          } else if ($subSelectColumn instanceof JsonArrayAgg) {
+            $columnAlias = $subSelectColumn->getAlias();
+          }
+
+          if ($columnAlias) {
+            $selectValues[] = "($subSelect) as $columnAlias";
+          } else {
+            $selectValues[] = "($subSelect)";
+          }
+        }
+      } else {
+        $selectValues[] = $this->sql->addValue($value, $params);
+      }
+    }
+
+    $tables = $this->getTables();
+    $selectValues = implode(",", $selectValues);
+
+    if (!$tables) {
+      return "SELECT $selectValues";
+    }
+
+    $tables = $this->sql->tableName($tables);
+    $where = $this->sql->getWhereClause($this->getConditions(), $params);
+    $havingClause = "";
+    if (count($this->havings) > 0) {
+      $havingClause  = " HAVING " . $this->sql->buildCondition($this->getHavings(), $params);
+    }
+
+    $joinStr = "";
+    $joins = $this->getJoins();
+    if (!empty($joins)) {
+      foreach ($joins as $join) {
+        $type = $join->getType();
+        $joinTable = $this->sql->tableName($join->getTable());
+        $tableAlias = ($join->getTableAlias() ? " " . $join->getTableAlias() : "");
+        $condition = $this->sql->buildCondition($join->getConditions(), $params);
+        $joinStr .= " $type JOIN $joinTable$tableAlias ON ($condition)";
+      }
+    }
+
+    $groupBy = "";
+    $groupColumns = $this->getGroupBy();
+    if (!empty($groupColumns)) {
+      $groupBy = " GROUP BY " . $this->sql->columnName($groupColumns);
+    }
+
+    $orderBy = "";
+    $orderColumns = $this->getOrderBy();
+    if (!empty($orderColumns)) {
+      $orderBy = " ORDER BY " . $this->sql->columnName($orderColumns);
+      $orderBy .= ($this->isOrderedAscending() ? " ASC" : " DESC");
+    }
+
+    $limit = ($this->getLimit() > 0 ? (" LIMIT " . $this->getLimit()) : "");
+    $offset = ($this->getOffset() > 0 ? (" OFFSET " . $this->getOffset()) : "");
+    $forUpdate = ($this->forUpdate ? " FOR UPDATE" : "");
+    return "SELECT $selectValues FROM $tables$joinStr$where$groupBy$havingClause$orderBy$limit$offset$forUpdate";
+  }
+}

Core/Driver/SQL/Query/StartTransaction.class.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\SQL;
+
+class StartTransaction extends Query {
+  public function __construct(SQL $sql) {
+    parent::__construct($sql);
+  }
+
+  public function build(array &$params): ?string {
+    return "START TRANSACTION";
+  }
+}

Core/Driver/SQL/Query/Truncate.class.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\SQL;
+
+class Truncate extends Query {
+
+  private string $tableName;
+
+  public function __construct(SQL $sql, string $name) {
+    parent::__construct($sql);
+    $this->tableName = $name;
+  }
+
+  public function getTable(): string { return $this->tableName; }
+
+  public function build(array &$params): ?string {
+    return "TRUNCATE " . $this->sql->tableName($this->getTable());
+  }
+}

Core/Driver/SQL/Query/Update.class.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Core\Driver\SQL\Query;
+
+use Core\Driver\SQL\Condition\CondOr;
+use Core\Driver\SQL\SQL;
+
+class Update extends Query {
+
+  private array $values;
+  private string $table;
+  private array $conditions;
+
+  public function __construct(SQL $sql, string $table) {
+    parent::__construct($sql);
+    $this->values = array();
+    $this->table = $table;
+    $this->conditions = array();
+  }
+
+  public function where(...$conditions): Update {
+    $this->conditions[] = (count($conditions) === 1 ? $conditions : new CondOr($conditions));
+    return $this;
+  }
+
+  public function set(string $key, $val): Update {
+    $this->values[$key] = $val;
+    return $this;
+  }
+
+  public function getTable(): string { return $this->table; }
+  public function getConditions(): array { return $this->conditions; }
+  public function getValues(): array { return $this->values; }
+
+  public function build(array &$params): ?string {
+    $table = $this->sql->tableName($this->getTable());
+
+    $valueStr = array();
+    foreach($this->getValues() as $key => $val) {
+      $valueStr[] = $this->sql->columnName($key) . "=" . $this->sql->addValue($val, $params);
+    }
+    $valueStr = implode(",", $valueStr);
+
+    $where = $this->sql->getWhereClause($this->getConditions(), $params);
+    return "UPDATE $table SET $valueStr$where";
+  }
+}

Core/Driver/SQL/RowIterator.class.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace Core\Driver\SQL;
+
+abstract class RowIterator implements \Iterator {
+
+  protected $resultSet;
+  protected int $rowIndex;
+  protected array $fetchedRows;
+  protected int $numRows;
+  protected bool $useCache;
+
+  public function __construct($resultSet, bool $useCache = false) {
+    $this->resultSet = $resultSet;
+    $this->fetchedRows = [];
+    $this->rowIndex = 0;
+    $this->numRows = $this->getNumRows();
+    $this->useCache = $useCache;
+  }
+
+  protected abstract function getNumRows(): int;
+  protected abstract function fetchRow(int $index): array;
+
+  public function current() {
+    return $this->fetchRow($this->rowIndex);
+  }
+
+  public function next() {
+    $this->rowIndex++;
+  }
+
+  public function key() {
+    return $this->rowIndex;
+  }
+
+  public function valid(): bool {
+    return $this->rowIndex < $this->numRows;
+  }
+}

Core/Driver/SQL/SQL.class.php

@@ -0,0 +1,434 @@
+<?php
+
+namespace Core\Driver\SQL;
+
+use Core\Driver\Logger\Logger;
+use Core\Driver\SQL\Column\Column;
+use Core\Driver\SQL\Condition\Compare;
+use Core\Driver\SQL\Condition\CondAnd;
+use Core\Driver\SQL\Condition\CondBool;
+use Core\Driver\SQL\Condition\CondIn;
+use Core\Driver\SQL\Condition\Condition;
+use Core\Driver\SQL\Condition\CondKeyword;
+use Core\Driver\SQL\Condition\CondNot;
+use Core\Driver\Sql\Condition\CondNull;
+use Core\Driver\SQL\Condition\CondOr;
+use Core\Driver\SQL\Condition\Exists;
+use Core\Driver\SQL\Constraint\Constraint;
+use Core\Driver\SQL\Constraint\Unique;
+use Core\Driver\SQL\Constraint\PrimaryKey;
+use Core\Driver\SQL\Constraint\ForeignKey;
+use Core\Driver\SQL\Expression\CaseWhen;
+use Core\Driver\SQL\Expression\CurrentTimeStamp;
+use Core\Driver\SQL\Expression\Expression;
+use Core\Driver\SQL\Expression\Sum;
+use Core\Driver\SQL\Query\AlterTable;
+use Core\Driver\SQL\Query\CreateProcedure;
+use Core\Driver\SQL\Query\CreateTable;
+use Core\Driver\SQL\Query\CreateTrigger;
+use Core\Driver\SQL\Query\Delete;
+use Core\Driver\SQL\Query\Drop;
+use Core\Driver\SQL\Query\Insert;
+use Core\Driver\SQL\Query\Query;
+use Core\Driver\SQL\Query\Select;
+use Core\Driver\SQL\Query\Truncate;
+use Core\Driver\SQL\Query\Update;
+use Core\Driver\SQL\Strategy\CascadeStrategy;
+use Core\Driver\SQL\Strategy\SetDefaultStrategy;
+use Core\Driver\SQL\Strategy\SetNullStrategy;
+use Core\Driver\SQL\Strategy\Strategy;
+use Core\Objects\ConnectionData;
+
+abstract class SQL {
+
+  const FETCH_NONE = 0;
+  const FETCH_ONE = 1;
+  const FETCH_ALL = 2;
+  const FETCH_ITERATIVE = 3;
+
+  protected Logger $logger;
+  protected string $lastError;
+  protected $connection;
+  protected ConnectionData $connectionData;
+  protected int $lastInsertId;
+
+  protected bool $logQueries;
+
+  public function __construct($connectionData) {
+    $this->connection = NULL;
+    $this->lastError = 'Unknown Error';
+    $this->connectionData = $connectionData;
+    $this->lastInsertId = 0;
+    $this->logger = new Logger(getClassName($this), $this);
+    $this->logQueries = false;
+  }
+
+  public function isConnected(): bool {
+    return !is_null($this->connection) && !is_bool($this->connection);
+  }
+
+  public function getLastError(): string {
+    return trim($this->lastError);
+  }
+
+  public function createTable($tableName): CreateTable {
+    return new CreateTable($this, $tableName);
+  }
+
+  public function insert($tableName, $columns=array()): Insert {
+    return new Insert($this, $tableName, $columns);
+  }
+
+  public function select(...$columNames): Select {
+    return new Select($this, $columNames);
+  }
+
+  public function truncate($table): Truncate {
+    return new Truncate($this, $table);
+  }
+
+  public function delete($table): Delete {
+    return new Delete($this, $table);
+  }
+
+  public function update($table): Update {
+    return new Update($this, $table);
+  }
+
+  public function drop(string $table): Drop {
+    return new Drop($this, $table);
+  }
+
+  public function alterTable($tableName): AlterTable {
+    return new AlterTable($this, $tableName);
+  }
+
+  public function createTrigger($triggerName): CreateTrigger {
+    return new CreateTrigger($this, $triggerName);
+  }
+
+  public function createProcedure(string $procName): CreateProcedure {
+    return new CreateProcedure($this, $procName);
+  }
+
+
+  // ####################
+  // ### ABSTRACT METHODS
+  // ####################
+
+  // Misc
+  public abstract function checkRequirements();
+  public abstract function getDriverName();
+
+  // Connection Management
+  public abstract function connect();
+  public abstract function disconnect();
+
+  /**
+   * @param Query $query
+   * @param int $fetchType
+   * @return mixed
+   */
+  public function executeQuery(Query $query, int $fetchType = self::FETCH_NONE) {
+
+    $parameters = [];
+    $queryStr = $query->build($parameters);
+
+    if ($query->dump) {
+      var_dump($queryStr);
+      var_dump($parameters);
+    }
+
+    if ($queryStr === null) {
+      return false;
+    }
+
+    $res = $this->execute($queryStr, $parameters, $fetchType);
+    $success = ($res !== FALSE);
+
+    // fetch generated serial ids for Insert statements
+    $generatedColumn = ($query instanceof Insert ? $query->getReturning() : null);
+    if ($success && $generatedColumn) {
+      $this->fetchReturning($res, $generatedColumn);
+    }
+
+    if ($this->logQueries && (!($query instanceof Insert) || $query->getTableName() !== "SystemLog")) {
+
+      if ($success === false || $fetchType == self::FETCH_NONE) {
+        $result = var_export($success, true);
+      } else if ($fetchType === self::FETCH_ALL) {
+        $result = count($res) . " rows";
+      } else if ($fetchType === self::FETCH_ONE) {
+        $result = ($res === null ? "(empty)" : "1 row");
+      } else if ($fetchType === self::FETCH_ITERATIVE) {
+        $result = $res->getNumRows() .  " rows (iterative)";
+      } else {
+        $result = "Unknown";
+      }
+
+      $message = sprintf("Query: %s, Parameters: %s, Result: %s",
+        var_export($queryStr, true), var_export($parameters, true), $result
+      );
+
+      if ($success === false) {
+        $message .= "Error: " . var_export($this->lastError, true);
+      }
+
+      $this->logger->debug($message);
+    }
+
+    return $fetchType === self::FETCH_NONE ? $success : $res;
+  }
+
+  public function getWhereClause($conditions, &$params): string {
+    if (!$conditions) {
+      return "";
+    } else {
+      return " WHERE " . $this->buildCondition($conditions, $params);
+    }
+  }
+
+  public function getConstraintDefinition(Constraint $constraint): ?string {
+    $columnName = $this->columnName($constraint->getColumnNames());
+
+    if ($constraint instanceof PrimaryKey) {
+      return "PRIMARY KEY ($columnName)";
+    } else if ($constraint instanceof Unique) {
+      return "UNIQUE ($columnName)";
+    } else if ($constraint instanceof ForeignKey) {
+      $refTable = $this->tableName($constraint->getReferencedTable());
+      $refColumn = $this->columnName($constraint->getReferencedColumn());
+      $strategy = $constraint->onDelete();
+      $code = "FOREIGN KEY ($columnName) REFERENCES $refTable ($refColumn)";
+      if ($strategy instanceof SetDefaultStrategy) {
+        $code .= " ON DELETE SET DEFAULT";
+      } else if($strategy instanceof SetNullStrategy) {
+        $code .= " ON DELETE SET NULL";
+      } else if($strategy instanceof CascadeStrategy) {
+        $code .= " ON DELETE CASCADE";
+      }
+
+      return $code;
+    } else {
+      $this->lastError = $this->logger->error("Unsupported constraint type: " . get_class($constraint));
+      return null;
+    }
+  }
+
+  protected abstract function fetchReturning($res, string $returningCol);
+  public abstract function getColumnDefinition(Column $column): ?string;
+  public abstract function getOnDuplicateStrategy(?Strategy $strategy, &$params): ?string;
+  public abstract function createTriggerBody(CreateTrigger $trigger, array $params = []): ?string;
+  public abstract function getProcedureHead(CreateProcedure $procedure): ?string;
+  public abstract function getColumnType(Column $column): ?string;
+  public function getProcedureTail(): string { return ""; }
+  public function getReturning(?string $columns): string { return ""; }
+
+  public function getProcedureBody(CreateProcedure $procedure): string {
+    $statements = "";
+    foreach ($procedure->getStatements() as $statement) {
+      $statements .= $this->buildUnsafe($statement) . ";";
+    }
+    return $statements;
+  }
+
+  protected function getUnsafeValue($value): ?string {
+    if (is_string($value)) {
+      return "'" . addslashes("$value") . "'"; // unsafe operation here...
+    } else if (is_numeric($value) || is_bool($value)) {
+      return $value;
+    } else if ($value instanceof Column) {
+      return $this->columnName($value);
+    } else if ($value === null) {
+      return "NULL";
+    } else {
+      $this->lastError = $this->logger->error("Cannot create unsafe value of type: " . gettype($value));
+      return null;
+    }
+  }
+
+  protected abstract function getValueDefinition($val);
+  public abstract function addValue($val, &$params = NULL, bool $unsafe = false);
+  protected abstract function buildUnsafe(Query $statement): string;
+
+  public abstract function tableName($table): string;
+  public abstract function columnName($col): string;
+
+  // Special Keywords and functions
+  public function now(): CurrentTimeStamp { return new CurrentTimeStamp(); }
+  public function currentTimestamp(): CurrentTimeStamp { return new CurrentTimeStamp(); }
+
+  public function count($col = NULL): Keyword {
+    if (is_null($col)) {
+      return new Keyword("COUNT(*) AS count");
+    } else if($col instanceof Keyword) {
+      return new Keyword("COUNT(" . $col->getValue() . ") AS count");
+    } else {
+      $countCol = strtolower(str_replace(".","_", $col)) .  "_count";
+      $col = $this->columnName($col);
+      return new Keyword("COUNT($col) AS $countCol");
+    }
+  }
+
+  public function distinct($col): Keyword {
+    $col = $this->columnName($col);
+    return new Keyword("DISTINCT($col)");
+  }
+
+  // Statements
+  /**
+   * @return mixed
+   */
+  protected abstract function execute($query, $values = NULL, int $fetchType = self::FETCH_NONE);
+
+  public function buildCondition($condition, &$params) {
+
+    if ($condition instanceof CondOr) {
+      $conditions = array();
+      foreach($condition->getConditions() as $cond) {
+        $conditions[] = $this->buildCondition($cond, $params);
+      }
+      return "(" . implode(" OR ", $conditions) . ")";
+    } else if ($condition instanceof CondAnd) {
+      $conditions = array();
+      foreach($condition->getConditions() as $cond) {
+        $conditions[] = $this->buildCondition($cond, $params);
+      }
+      return "(" . implode(" AND ", $conditions) . ")";
+    } else if ($condition instanceof Compare) {
+      $column = $this->columnName($condition->getColumn());
+      $value = $condition->getValue();
+      $operator = $condition->getOperator();
+
+      if ($value === null) {
+        if ($operator === "=") {
+          return "$column IS NULL";
+        } else if ($operator === "!=") {
+          return "$column IS NOT NULL";
+        }
+      }
+
+      return $column . $operator . $this->addValue($value, $params);
+    } else if ($condition instanceof CondBool) {
+      return $this->columnName($condition->getValue());
+    } else if (is_array($condition)) {
+      if (count($condition) === 1) {
+        return $this->buildCondition($condition[0], $params);
+      } else {
+        $conditions = array();
+        foreach ($condition as $cond) {
+          $conditions[] = $this->buildCondition($cond, $params);
+        }
+        return implode(" AND ", $conditions);
+      }
+    } else if($condition instanceof CondIn) {
+
+      $needle = $condition->getNeedle();
+      $haystack = $condition->getHaystack();
+      if (is_array($haystack)) {
+        $values = array();
+        foreach ($haystack as $value) {
+          $values[] = $this->addValue($value, $params);
+        }
+
+        $values = implode(",", $values);
+      } else if($haystack instanceof Select) {
+        $values = $haystack->build($params);
+      } else {
+        $this->lastError = $this->logger->error("Unsupported in-expression value: " . get_class($condition));
+        return false;
+      }
+
+      if ($needle instanceof Column) {
+        $lhs = $this->createExpression($needle, $params);
+      } else {
+        $lhs = $this->addValue($needle, $params);
+      }
+
+      return "$lhs IN ($values)";
+    } else if($condition instanceof CondKeyword) {
+      $left = $condition->getLeftExp();
+      $right = $condition->getRightExp();
+      $keyword = $condition->getKeyword();
+      $left = ($left instanceof Column) ? $this->columnName($left->getName()) : $this->addValue($left, $params);
+      $right = ($right instanceof Column) ? $this->columnName($right->getName()) : $this->addValue($right, $params);
+      return "$left $keyword $right ";
+    } else if($condition instanceof CondNot) {
+      $expression = $condition->getExpression();
+      if ($expression instanceof Condition) {
+        $expression = $this->buildCondition($expression, $params);
+      } else {
+        $expression = $this->columnName($expression);
+      }
+
+      return "NOT $expression";
+    } else if ($condition instanceof CondNull) {
+        return $this->columnName($condition->getColumn()) . " IS NULL";
+    } else if ($condition instanceof Exists) {
+        return "EXISTS(" .$condition->getSubQuery()->build($params) . ")";
+    } else {
+      $this->lastError = $this->logger->error("Unsupported condition type: " . gettype($condition));
+      return null;
+    }
+  }
+
+  protected function createExpression(Expression $exp, array &$params): ?string {
+    if ($exp instanceof Column) {
+      return $this->columnName($exp->getName());
+    } else if ($exp instanceof Query) {
+      return "(" . $exp->build($params) . ")";
+    } else if ($exp instanceof CaseWhen) {
+      $condition = $this->buildCondition($exp->getCondition(), $params);
+
+      // psql requires constant values here
+      $trueCase = $this->addValue($exp->getTrueCase(), $params, true);
+      $falseCase = $this->addValue($exp->getFalseCase(), $params, true);
+
+      return "CASE WHEN $condition THEN $trueCase ELSE $falseCase END";
+    } else if ($exp instanceof Sum) {
+      $value = $this->addValue($exp->getValue(), $params);
+      $alias = $this->columnName($exp->getAlias());
+      return "SUM($value) AS $alias";
+    } else {
+      $this->lastError = $this->logger->error("Unsupported expression type: " . get_class($exp));
+      return null;
+    }
+  }
+
+  public function setLastError($str) {
+    $this->lastError = $str;
+  }
+
+  public function getLastInsertId(): int {
+    return $this->lastInsertId;
+  }
+
+  public function close() {
+    $this->disconnect();
+    $this->connection = NULL;
+  }
+
+  public static function createConnection(ConnectionData $connectionData) {
+    $type = $connectionData->getProperty("type");
+    if ($type === "mysql") {
+      $sql = new MySQL($connectionData);
+    } else if ($type === "postgres") {
+      $sql = new PostgreSQL($connectionData);
+    } else {
+      Logger::instance()->error("Unknown database type: $type");
+      return "Unknown database type";
+    }
+
+    if ($sql->checkRequirements()) {
+      $sql->connect();
+    }
+
+    return $sql;
+  }
+
+  public abstract function getStatus();
+
+  public function parseBool($val) : bool {
+    return in_array($val, array(true, 1, '1', 't', 'true', 'TRUE'), true);
+  }
+}

Core/Driver/SQL/Strategy/CascadeStrategy.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Strategy;
+
+class CascadeStrategy extends Strategy {
+
+  public function __construct() {
+  }
+
+}

Core/Driver/SQL/Strategy/SetDefaultStrategy.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Strategy;
+
+class SetDefaultStrategy extends Strategy {
+
+  public function __construct() {
+  }
+
+}

Core/Driver/SQL/Strategy/SetNullStrategy.class.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Core\Driver\SQL\Strategy;
+
+class SetNullStrategy extends Strategy {
+
+  public function __construct() {
+  }
+
+}

Core/Driver/SQL/Strategy/Strategy.class.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace Core\Driver\SQL\Strategy;
+
+abstract class Strategy {
+
+}

Core/Driver/SQL/Strategy/UpdateStrategy.class.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Core\Driver\SQL\Strategy;
+
+class UpdateStrategy extends Strategy {
+
+  private array $values;
+  private array $conflictingColumns;
+
+  public function __construct(array $conflictingColumns, array $values) {
+    $this->conflictingColumns = $conflictingColumns;
+    $this->values = $values;
+  }
+
+  public function getConflictingColumns(): array {
+    return $this->conflictingColumns;
+  }
+
+  public function getValues(): array {
+    return $this->values;
+  }
+}

Core/Driver/SQL/Type/CurrentColumn.php

@@ -0,0 +1,14 @@
+<?php
+
+
+namespace Core\Driver\SQL\Type;
+
+
+use Core\Driver\SQL\Column\Column;
+
+class CurrentColumn extends Column {
+
+  public function __construct(string $string) {
+    parent::__construct($string);
+  }
+}

Core/Driver/SQL/Type/CurrentTable.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Type;
+
+use Core\Driver\SQL\Column\StringColumn;
+
+class CurrentTable extends StringColumn {
+  public function __construct() {
+    parent::__construct("CURRENT_TABLE");
+  }
+}

Core/Driver/SQL/Type/Trigger.class.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Core\Driver\SQL\Type;
+
+use Core\Driver\SQL\Keyword;
+
+class Trigger extends Keyword {
+  public function __construct() {
+    parent::__construct("TRIGGER");
+  }
+}