diff --git a/core/Api/ContactAPI.class.php b/core/Api/ContactAPI.class.php
index eed1bbe..599a3ac 100644
--- a/core/Api/ContactAPI.class.php
+++ b/core/Api/ContactAPI.class.php
@@ -95,8 +95,6 @@ namespace Api\Contact {
         if (!$insertDB) {
           $message .= " Mail: $dbError";
         }
-
-        error_log($message);
       }
 
       if (!$sendMail && !$insertDB) {
diff --git a/core/Api/MailAPI.class.php b/core/Api/MailAPI.class.php
index c8d7f72..ac9a5a8 100644
--- a/core/Api/MailAPI.class.php
+++ b/core/Api/MailAPI.class.php
@@ -182,13 +182,14 @@ namespace Api\Mail {
         $this->success = @$mail->Send();
         if (!$this->success) {
           $this->lastError = "Error sending Mail: $mail->ErrorInfo";
-          error_log("sendMail() failed: $mail->ErrorInfo");
+          $this->logger->error("sendMail() failed: $mail->ErrorInfo");
         } else {
           $this->result["messageId"] = $mail->getLastMessageID();
         }
       } catch (Exception $e) {
         $this->success = false;
         $this->lastError = "Error sending Mail: $e";
+        $this->logger->error($this->lastError);
       }
 
       return $this->success;
diff --git a/core/Api/Request.class.php b/core/Api/Request.class.php
index 4f94ea4..b10ed49 100644
--- a/core/Api/Request.class.php
+++ b/core/Api/Request.class.php
@@ -6,6 +6,12 @@ use Driver\Logger\Logger;
 use Objects\User;
 use PhpMqtt\Client\MqttClient;
 
+/**
+ * TODO: we need following features, probably as abstract/generic class/method:
+ * - easy way for pagination (select with limit/offset)
+ * - CRUD Endpoints/Objects (Create, Update, Delete)
+ */
+
 abstract class Request {
 
   protected User $user;
diff --git a/core/Api/Stats.class.php b/core/Api/Stats.class.php
index 815611a..ebfb61d 100644
--- a/core/Api/Stats.class.php
+++ b/core/Api/Stats.class.php
@@ -35,7 +35,7 @@ class Stats extends Request {
     return ($this->success ? $res[0]["count"] : 0);
   }
 
-  private function checkSettings() {
+  private function checkSettings(): bool {
     $req = new \Api\Settings\Get($this->user);
     $this->success = $req->execute(array("key" => "^(mail_enabled|recaptcha_enabled)$"));
     $this->lastError = $req->getLastError();
diff --git a/core/Api/VerifyCaptcha.class.php b/core/Api/VerifyCaptcha.class.php
index f702d2c..2345ab3 100644
--- a/core/Api/VerifyCaptcha.class.php
+++ b/core/Api/VerifyCaptcha.class.php
@@ -17,10 +17,10 @@ class VerifyCaptcha extends Request {
   }
 
   public function _execute(): bool {
-     $settings = $this->user->getConfiguration()->getSettings();
-     if (!$settings->isRecaptchaEnabled()) {
-       return $this->createError("Google reCaptcha is not enabled.");
-     }
+    $settings = $this->user->getConfiguration()->getSettings();
+    if (!$settings->isRecaptchaEnabled()) {
+      return $this->createError("Google reCaptcha is not enabled.");
+    }
 
     $url = "https://www.google.com/recaptcha/api/siteverify";
     $secret = $settings->getRecaptchaSecretKey();
@@ -33,12 +33,12 @@ class VerifyCaptcha extends Request {
     );
 
     $ch = curl_init();
-    curl_setopt($ch, CURLOPT_URL,$url);
+    curl_setopt($ch, CURLOPT_URL, $url);
     curl_setopt($ch, CURLOPT_POST, 1);
     curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($params));
     curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
     $response = @json_decode(curl_exec($ch), true);
-    curl_close ($ch);
+    curl_close($ch);
 
     $this->success = false;
     $this->lastError = "Could not verify captcha: No response from google received.";
@@ -49,10 +49,9 @@ class VerifyCaptcha extends Request {
         $this->lastError = "Could not verify captcha: " . implode(";", $response["error-codes"]);
       } else {
         $score = $response["score"];
-        if($action !== $response["action"]) {
+        if ($action !== $response["action"]) {
           $this->createError("Could not verify captcha: Action does not match");
-        }
-        else if($score < 0.7) {
+        } else if ($score < 0.7) {
           $this->createError("Could not verify captcha: Google ReCaptcha Score < 0.7 (Your score: $score), you are likely a bot");
         }
       }
diff --git a/core/Configuration/CreateDatabase.class.php b/core/Configuration/CreateDatabase.class.php
index 2720139..73869b7 100644
--- a/core/Configuration/CreateDatabase.class.php
+++ b/core/Configuration/CreateDatabase.class.php
@@ -8,9 +8,6 @@ use \Driver\SQL\Strategy\CascadeStrategy;
 
 class CreateDatabase extends DatabaseScript {
 
-  // NOTE:
-  // explicit serial ids removed due to postgres' serial implementation
-
   public static function createQueries(SQL $sql): array {
     $queries = array();
 
diff --git a/core/Driver/SQL/Column/BigIntColumn.php b/core/Driver/SQL/Column/BigIntColumn.class.php
similarity index 79%
rename from core/Driver/SQL/Column/BigIntColumn.php
rename to core/Driver/SQL/Column/BigIntColumn.class.php
index d63fec2..a065f31 100644
--- a/core/Driver/SQL/Column/BigIntColumn.php
+++ b/core/Driver/SQL/Column/BigIntColumn.class.php
@@ -1,8 +1,6 @@
 <?php
 
-namespace Driver\SQL\Query;
-
-use Driver\SQL\Column\IntColumn;
+namespace Driver\SQL\Column;
 
 class BigIntColumn extends IntColumn {
 
diff --git a/core/Driver/SQL/Column/DoubleColumn.class.php b/core/Driver/SQL/Column/DoubleColumn.class.php
new file mode 100644
index 0000000..3f7c5d6
--- /dev/null
+++ b/core/Driver/SQL/Column/DoubleColumn.class.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace 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";
+  }
+}
\ No newline at end of file
diff --git a/core/Driver/SQL/Column/FloatColumn.class.php b/core/Driver/SQL/Column/FloatColumn.class.php
new file mode 100644
index 0000000..fa7408c
--- /dev/null
+++ b/core/Driver/SQL/Column/FloatColumn.class.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace 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";
+  }
+}
\ No newline at end of file
diff --git a/core/Driver/SQL/Column/NumericColumn.class.php b/core/Driver/SQL/Column/NumericColumn.class.php
new file mode 100644
index 0000000..6c92eb0
--- /dev/null
+++ b/core/Driver/SQL/Column/NumericColumn.class.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Driver\SQL\Column;
+
+use 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 $this->type;
+  }
+}
\ No newline at end of file
diff --git a/core/Driver/SQL/MySQL.class.php b/core/Driver/SQL/MySQL.class.php
index e97d4f4..fff0bb6 100644
--- a/core/Driver/SQL/MySQL.class.php
+++ b/core/Driver/SQL/MySQL.class.php
@@ -7,6 +7,7 @@ use \Api\Parameter\Parameter;
 use DateTime;
 use \Driver\SQL\Column\Column;
 use \Driver\SQL\Column\IntColumn;
+use Driver\SQL\Column\NumericColumn;
 use \Driver\SQL\Column\SerialColumn;
 use \Driver\SQL\Column\StringColumn;
 use \Driver\SQL\Column\EnumColumn;
@@ -267,6 +268,19 @@ class MySQL extends SQL {
       return "BOOLEAN";
     } else if ($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;
diff --git a/core/Driver/SQL/PostgreSQL.class.php b/core/Driver/SQL/PostgreSQL.class.php
index 5a53943..35f5733 100644
--- a/core/Driver/SQL/PostgreSQL.class.php
+++ b/core/Driver/SQL/PostgreSQL.class.php
@@ -6,6 +6,7 @@ use \Api\Parameter\Parameter;
 
 use Driver\SQL\Column\Column;
 use \Driver\SQL\Column\IntColumn;
+use Driver\SQL\Column\NumericColumn;
 use \Driver\SQL\Column\SerialColumn;
 use \Driver\SQL\Column\StringColumn;
 use \Driver\SQL\Column\EnumColumn;
@@ -33,7 +34,7 @@ use Driver\SQL\Type\Trigger;
 class PostgreSQL extends SQL {
 
   public function __construct($connectionData) {
-     parent::__construct($connectionData);
+    parent::__construct($connectionData);
   }
 
   public function checkRequirements() {
@@ -46,7 +47,7 @@ class PostgreSQL extends SQL {
 
   // Connection Management
   public function connect() {
-    if(!is_null($this->connection)) {
+    if (!is_null($this->connection)) {
       return true;
     }
 
@@ -59,7 +60,7 @@ class PostgreSQL extends SQL {
     );
 
     $connectionString = array();
-    foreach($config as $key => $val) {
+    foreach ($config as $key => $val) {
       if (!empty($val)) {
         $connectionString[] = "$key=$val";
       }
@@ -77,7 +78,7 @@ class PostgreSQL extends SQL {
   }
 
   public function disconnect() {
-    if(is_null($this->connection))
+    if (is_null($this->connection))
       return;
 
     @pg_close($this->connection);
@@ -102,9 +103,9 @@ class PostgreSQL extends SQL {
     $pgParams = array();
 
     if (!is_null($values)) {
-      foreach($values as $value) {
+      foreach ($values as $value) {
         $paramType = Parameter::parseType($value);
-        switch($paramType) {
+        switch ($paramType) {
           case Parameter::TYPE_DATE:
             $value = $value->format("Y-m-d");
             break;
@@ -154,35 +155,35 @@ class PostgreSQL extends SQL {
   }
 
   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, $parameters);
-            }
+    if (!is_null($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;
         }
+
+        $conflictingColumns = $this->columnName($strategy->getConflictingColumns());
+        $updateValues = implode(",", $updateValues);
+        return " ON CONFLICT ($conflictingColumns) DO UPDATE SET $updateValues";
       } else {
-        return "";
+        $strategyClass = get_class($strategy);
+        $this->lastError = $this->logger->error("ON DUPLICATE Strategy $strategyClass is not supported yet.");
+        return null;
       }
+    } else {
+      return "";
+    }
   }
 
   public function getReturning(?string $columns): string {
@@ -205,7 +206,7 @@ class PostgreSQL extends SQL {
   // UGLY but.. what should i do?
   private function createEnum(EnumColumn $enumColumn, string $typeName): string {
     $values = array();
-    foreach($enumColumn->getValues() as $value) {
+    foreach ($enumColumn->getValues() as $value) {
       $values[] = $this->getValueDefinition($value);
     }
 
@@ -228,22 +229,33 @@ class PostgreSQL extends SQL {
       } else {
         return "TEXT";
       }
-    } else if($column instanceof SerialColumn) {
+    } else if ($column instanceof SerialColumn) {
       return "SERIAL";
-    } else if($column instanceof IntColumn) {
+    } else if ($column instanceof IntColumn) {
       return $column->getType();
-    } else if($column instanceof DateTimeColumn) {
+    } else if ($column instanceof DateTimeColumn) {
       return "TIMESTAMP";
-    } else if($column instanceof EnumColumn) {
+    } else if ($column instanceof EnumColumn) {
       $typeName = $column->getName();
-      if(!endsWith($typeName, "_type")) {
+      if (!endsWith($typeName, "_type")) {
         $typeName = "${typeName}_type";
       }
       return $typeName;
-    } else if($column instanceof BoolColumn) {
+    } else if ($column instanceof BoolColumn) {
       return "BOOLEAN";
-    } else if($column instanceof JsonColumn) {
+    } 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;
@@ -274,9 +286,9 @@ class PostgreSQL extends SQL {
   protected function getValueDefinition($value) {
     if (is_numeric($value)) {
       return $value;
-    } else if(is_bool($value)) {
+    } else if (is_bool($value)) {
       return $value ? "TRUE" : "FALSE";
-    } else if(is_null($value)) {
+    } else if (is_null($value)) {
       return "NULL";
     } else if ($value instanceof Keyword) {
       return $value->getValue();
@@ -312,7 +324,7 @@ class PostgreSQL extends SQL {
   public function tableName($table): string {
     if (is_array($table)) {
       $tables = array();
-      foreach($table as $t) $tables[] = $this->tableName($t);
+      foreach ($table as $t) $tables[] = $this->tableName($t);
       return implode(",", $tables);
     } else {
       $parts = explode(" ", $table);
@@ -328,15 +340,17 @@ class PostgreSQL extends SQL {
   public function columnName($col): string {
     if ($col instanceof KeyWord) {
       return $col->getValue();
-    } elseif(is_array($col)) {
-      $columns = array_map(function ($c) { return $this->columnName($c); }, $col);
+    } elseif (is_array($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($col, " as ")) !== FALSE) {
+      } else if (($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";
@@ -358,7 +372,7 @@ class PostgreSQL extends SQL {
   }
 
   public function buildCondition($condition, &$params) {
-    if($condition instanceof CondRegex) {
+    if ($condition instanceof CondRegex) {
       $left = $condition->getLeftExp();
       $right = $condition->getRightExp();
       $left = ($left instanceof Column) ? $this->columnName($left->getName()) : $this->addValue($left, $params);
@@ -372,7 +386,7 @@ class PostgreSQL extends SQL {
   private function createTriggerProcedure(string $name, array $statements) {
     $params = [];
     $query = "CREATE OR REPLACE FUNCTION $name() RETURNS TRIGGER AS \$table\$ BEGIN ";
-    foreach($statements as $stmt) {
+    foreach ($statements as $stmt) {
       if ($stmt instanceof Keyword) {
         $query .= $stmt->getValue() . ";";
       } else {
diff --git a/core/Driver/SQL/Query/CreateTable.class.php b/core/Driver/SQL/Query/CreateTable.class.php
index a3c9e6d..37aab82 100644
--- a/core/Driver/SQL/Query/CreateTable.class.php
+++ b/core/Driver/SQL/Query/CreateTable.class.php
@@ -2,6 +2,11 @@
 
 namespace Driver\SQL\Query;
 
+use Driver\SQL\Column\BigIntColumn;
+use Driver\SQL\Column\Column;
+use Driver\SQL\Column\DoubleColumn;
+use Driver\SQL\Column\FloatColumn;
+use Driver\SQL\Column\NumericColumn;
 use Driver\SQL\Column\SerialColumn;
 use Driver\SQL\Column\StringColumn;
 use Driver\SQL\Column\IntColumn;
@@ -10,6 +15,7 @@ use Driver\SQL\Column\EnumColumn;
 use Driver\SQL\Column\BoolColumn;
 use Driver\SQL\Column\JsonColumn;
 
+use Driver\SQL\Constraint\Constraint;
 use Driver\SQL\Constraint\PrimaryKey;
 use Driver\SQL\Constraint\Unique;
 use Driver\SQL\Constraint\ForeignKey;
@@ -31,6 +37,16 @@ class CreateTable extends Query {
     $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;
@@ -71,6 +87,21 @@ class CreateTable extends Query {
     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 {
     $this->constraints[] = new PrimaryKey($names);
     return $this;
diff --git a/core/Objects/DatabaseEntity/DatabaseEntity.class.php b/core/Objects/DatabaseEntity/DatabaseEntity.class.php
new file mode 100644
index 0000000..25fccb8
--- /dev/null
+++ b/core/Objects/DatabaseEntity/DatabaseEntity.class.php
@@ -0,0 +1,75 @@
+<?php
+
+namespace Objects\DatabaseEntity;
+
+use Driver\Logger\Logger;
+use Driver\SQL\Condition\Condition;
+use Driver\SQL\SQL;
+
+abstract class DatabaseEntity {
+
+  private static array $handlers = [];
+  private ?int $id;
+
+  public function __construct() {
+    $this->id = null;
+  }
+
+  public static function find(SQL $sql, int $id): ?DatabaseEntity {
+    $handler = self::getHandler();
+    return $handler->fetchOne($sql, $id);
+  }
+
+  public static function findAll(SQL $sql, ?Condition $condition): ?array {
+    $handler = self::getHandler();
+    return $handler->fetchMultiple($sql, $condition);
+  }
+
+  public function save(SQL $sql): bool {
+    $handler = self::getHandler();
+    $res = $handler->insertOrUpdate($sql, $this);
+    if ($res === false) {
+      return false;
+    } else if ($this->id === null) {
+      $this->id = $res;
+    }
+
+    return true;
+  }
+
+  public function delete(SQL $sql): bool {
+    $handler = self::getHandler();
+    if ($this->id === null) {
+      $className = $handler->getReflection()->getName();
+      (new Logger("DatabaseEntity", $sql))->error("Cannot delete entity of class '$className' without id");
+      return false;
+    }
+
+    return $handler->delete($sql, $this->id);
+  }
+
+  public static function getHandler($obj_or_class = null): DatabaseEntityHandler {
+
+    if (!$obj_or_class) {
+      $obj_or_class = get_called_class();
+    }
+
+    if (!($obj_or_class instanceof \ReflectionClass)) {
+      $class = new \ReflectionClass($obj_or_class);
+    } else {
+      $class = $obj_or_class;
+    }
+
+    $handler = self::$handlers[$class->getShortName()] ?? null;
+    if (!$handler) {
+      $handler = new DatabaseEntityHandler($class);
+      self::$handlers[$class->getShortName()] = $handler;
+    }
+
+    return $handler;
+  }
+
+  public function getId(): ?int {
+    return $this->id;
+  }
+}
\ No newline at end of file
diff --git a/core/Objects/DatabaseEntity/DatabaseEntityHandler.php b/core/Objects/DatabaseEntity/DatabaseEntityHandler.php
new file mode 100644
index 0000000..3138601
--- /dev/null
+++ b/core/Objects/DatabaseEntity/DatabaseEntityHandler.php
@@ -0,0 +1,188 @@
+<?php
+
+namespace Objects\DatabaseEntity;
+
+use Driver\SQL\Column\BoolColumn;
+use Driver\SQL\Column\DateTimeColumn;
+use Driver\SQL\Column\IntColumn;
+use Driver\SQL\Column\StringColumn;
+use Driver\SQL\Condition\Compare;
+use Driver\SQL\Condition\Condition;
+use Driver\SQL\Column\DoubleColumn;
+use Driver\SQL\Column\FloatColumn;
+use Driver\SQL\Constraint\ForeignKey;
+use Driver\SQL\SQL;
+use Driver\SQL\Strategy\CascadeStrategy;
+use Driver\SQL\Strategy\SetNullStrategy;
+use PHPUnit\Util\Exception;
+
+class DatabaseEntityHandler {
+
+  private \ReflectionClass $entityClass;
+  private string $tableName;
+  private array $columns;
+  private array $properties;
+
+  public function __construct(\ReflectionClass $entityClass) {
+    $className = $entityClass->getName();
+    $this->entityClass = $entityClass;
+    if (!$this->entityClass->isSubclassOf(DatabaseEntity::class) ||
+      !$this->entityClass->isInstantiable()) {
+      throw new Exception("Cannot persist class '$className': Not an instance of DatabaseEntity or not instantiable.");
+    }
+
+    $this->tableName = $this->entityClass->getShortName();
+    $this->columns = [];
+    $this->properties = [];
+    $this->relations = [];
+
+    foreach ($this->entityClass->getProperties() as $property) {
+      $propertyName = $property->getName();
+      $propertyType = $property->getType();
+      $columnName = self::getColumnName($propertyName);
+      if (!($propertyType instanceof \ReflectionNamedType)) {
+        throw new Exception("Cannot persist class '$className': Property '$propertyName' has no valid type");
+      }
+
+      $nullable = $propertyType->allowsNull();
+      $propertyTypeName = $propertyType->getName();
+      if ($propertyTypeName === 'string') {
+        $this->columns[$propertyName] = new StringColumn($columnName, null, $nullable);
+      } else if ($propertyTypeName === 'int') {
+        $this->columns[$propertyName] = new IntColumn($columnName, $nullable);
+      } else if ($propertyTypeName === 'float') {
+        $this->columns[$propertyName] = new FloatColumn($columnName, $nullable);
+      } else if ($propertyTypeName === 'double') {
+        $this->columns[$propertyName] = new DoubleColumn($columnName, $nullable);
+      } else if ($propertyTypeName === 'bool') {
+        $this->columns[$propertyName] = new BoolColumn($columnName, $nullable);
+      } else if ($propertyTypeName === 'DateTime') {
+        $this->columns[$propertyName] = new DateTimeColumn($columnName, $nullable);
+      } else {
+        try {
+          $requestedClass = new \ReflectionClass($propertyTypeName);
+          if ($requestedClass->isSubclassOf(DatabaseEntity::class)) {
+            $requestedHandler = ($requestedClass->getName() === $this->entityClass->getName()) ?
+              $this : DatabaseEntity::getHandler($requestedClass);
+            $strategy = $nullable ? new SetNullStrategy() : new CascadeStrategy();
+            $this->columns[$propertyName] = new IntColumn($columnName, $nullable);
+            $this->relations[$propertyName] = new ForeignKey($columnName, $requestedHandler->tableName, "id", $strategy);
+          }
+        } catch (\Exception $ex) {
+          throw new Exception("Cannot persist class '$className': Property '$propertyName' has non persist-able type: $propertyTypeName");
+        }
+      }
+
+      $this->properties[$propertyName] = $property;
+    }
+  }
+
+  private static function getColumnName(string $propertyName): string {
+    // abcTestLOL => abc_test_lol
+    return strtolower(preg_replace_callback("/([a-z])([A-Z]+)/", function ($m) {
+      return $m[1] . "_" . strtolower($m[2]);
+    }, $propertyName));
+  }
+
+  public function getReflection(): \ReflectionClass {
+    return $this->entityClass;
+  }
+
+  private function entityFromRow(array $row): DatabaseEntity {
+    $entity = $this->entityClass->newInstanceWithoutConstructor();
+    foreach ($this->columns as $propertyName => $column) {
+      $this->properties[$propertyName]->setValue($entity, $row[$column]);
+    }
+    return $entity;
+  }
+
+  public function fetchOne(SQL $sql, int $id): ?DatabaseEntity {
+    $res = $sql->select(...array_keys($this->columns))
+      ->from($this->tableName)
+      ->where(new Compare("id", $id))
+      ->first()
+      ->execute();
+
+    if (empty($res)) {
+      return null;
+    } else {
+      return $this->entityFromRow($res);
+    }
+  }
+
+  public function fetchMultiple(SQL $sql, ?Condition $condition = null): ?array {
+    $query = $sql->select(...array_keys($this->columns))
+      ->from($this->tableName);
+
+    if ($condition) {
+      $query->where($condition);
+    }
+
+    $res = $query->execute();
+    if ($res === false) {
+      return null;
+    } else {
+      $entities = [];
+      foreach ($res as $row) {
+        $entities[] = $this->entityFromRow($row);
+      }
+      return $entities;
+    }
+  }
+
+  public function createTable(SQL $sql): bool {
+    $query = $sql->createTable($this->tableName)
+      ->onlyIfNotExists()
+      ->addSerial("id")
+      ->primaryKey("id");
+
+    foreach ($this->columns as $column) {
+      $query->addColumn($column);
+    }
+
+    foreach ($this->relations as $constraint) {
+      $query->addConstraint($constraint);
+    }
+
+    return $query->execute();
+  }
+
+  public function insertOrUpdate(SQL $sql, DatabaseEntity $entity) {
+    $id = $entity->getId();
+    if ($id === null) {
+      $columns = [];
+      $row = [];
+
+      foreach ($this->columns as $propertyName => $column) {
+        $columns[] = $column->getName();
+        $row[] = $this->properties[$propertyName]->getValue($entity);
+      }
+
+      $res = $sql->insert($this->tableName, $columns)
+        ->addRow(...$row)
+        ->returning("id")
+        ->execute();
+
+      if ($res !== false) {
+        return $sql->getLastInsertId();
+      } else {
+        return false;
+      }
+    } else {
+      $query = $sql->update($this->tableName)
+        ->where(new Compare("id", $id));
+
+      foreach ($this->columns as $propertyName => $column) {
+        $columnName = $column->getName();
+        $value = $this->properties[$propertyName]->getValue($entity);
+        $query->set($columnName, $value);
+      }
+
+      return $query->execute();
+    }
+  }
+
+  public function delete(SQL $sql, int $id) {
+    return $sql->delete($this->tableName)->where(new Compare("id", $id))->execute();
+  }
+}
\ No newline at end of file
diff --git a/core/core.php b/core/core.php
index c8b0e76..bd6d6d3 100644
--- a/core/core.php
+++ b/core/core.php
@@ -1,5 +1,10 @@
 <?php
 
+/**
+ * This file contains functions used globally without a namespace and should not require
+ * any other files. It also loads the composer vendor libraries.
+ */
+
 $autoLoad = implode(DIRECTORY_SEPARATOR, [__DIR__, "External", "vendor", "autoload.php"]);
 if (is_file($autoLoad)) {
   require_once $autoLoad;
@@ -186,10 +191,6 @@ function intendCode($code, $escape = true): string {
   return $newCode;
 }
 
-function replaceCssSelector($sel) {
-  return preg_replace("~[.#<>]~", "_", preg_replace("~[:\-]~", "", $sel));
-}
-
 function html_attributes(array $attributes): string {
   return implode(" ", array_map(function ($key) use ($attributes) {
     $value = htmlspecialchars($attributes[$key]);
diff --git a/test/DatabaseEntity.test.php b/test/DatabaseEntity.test.php
new file mode 100644
index 0000000..e69de29