diff --git a/php/model/DatabaseArticleManager.php b/php/model/DatabaseArticleManager.php
index 7745919..3d282a4 100644
--- a/php/model/DatabaseArticleManager.php
+++ b/php/model/DatabaseArticleManager.php
@@ -25,23 +25,26 @@ class DatabaseArticleManager implements ArticleManagerDAO {
 
                 // Tabelle für Beiträge
                 $db->exec("
-                    CREATE TABLE articles (
-                        id INTEGER PRIMARY KEY AUTOINCREMENT,
-                        title TEXT,
-                        content TEXT,
-                        author TEXT,
-                        category TEXT,
-                        tags TEXT,
-                        created TIMESTAMP DEFAULT CURRENT_TIMESTAMP
-                    );");
+                    CREATE TABLE IF NOT EXISTS articles (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    title TEXT,
+                    content TEXT,
+                    author TEXT,
+                    category TEXT,
+                    tags TEXT,
+                    created TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                    FOREIGN KEY (author) REFERENCES users(email) ON DELETE SET NULL ON UPDATE CASCADE
+                );");
+
 
                 // Tabelle für Likes
                 $db->exec("
-                CREATE TABLE likes (
+                CREATE TABLE IF NOT EXISTS likes (
                     article_id INTEGER,
                     user_id TEXT,
                     PRIMARY KEY (article_id, user_id),
-                    FOREIGN KEY (article_id) REFERENCES articles(id) ON DELETE CASCADE
+                    FOREIGN KEY (article_id) REFERENCES articles(id) ON DELETE CASCADE,
+                    FOREIGN KEY (user_id) REFERENCES users(email) ON DELETE CASCADE
                 );");
                 unset($db);
             } catch (PDOException $e) {
@@ -52,17 +55,22 @@ class DatabaseArticleManager implements ArticleManagerDAO {
 
     /**
      * Baut die Verbindung zur Datenbank auf.
-     * @throws InternalServerErrorException
+     *
+     * @return PDO Datenbankverbindung
+     * @throws RuntimeException
      */
     private function getConnection()
     {
         try {
-            $user = 'root';
-            $pw = null;
             $dsn = 'sqlite:' . __DIR__ . '/../../db/eduforgeDB.db';
-            return new PDO($dsn, $user, $pw);
+
+            $db = new PDO($dsn, null, null);
+            $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            $db->exec('PRAGMA foreign_keys = ON;');
+
+            return $db;
         } catch (PDOException $e) {
-            throw new InternalServerErrorException($e->getMessage());
+            throw new RuntimeException("internal_error");
         }
     }
 
diff --git a/php/model/DatabaseCommentManager.php b/php/model/DatabaseCommentManager.php
index 8228975..1ad537a 100644
--- a/php/model/DatabaseCommentManager.php
+++ b/php/model/DatabaseCommentManager.php
@@ -23,13 +23,16 @@ class DatabaseCommentManager implements CommentManagerDAO
 
             $db->exec("
                 CREATE TABLE IF NOT EXISTS comments (
-                    id INTEGER PRIMARY KEY AUTOINCREMENT,
-                    article_id INTEGER NOT NULL,
-                    parent_comment_id INTEGER NULL,
-                    author TEXT NOT NULL,
-                    content TEXT NOT NULL,
-                    created TIMESTAMP DEFAULT CURRENT_TIMESTAMP
-                );
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                article_id INTEGER NOT NULL,
+                parent_comment_id INTEGER NULL,
+                author TEXT NOT NULL,
+                content TEXT NOT NULL,
+                created TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                FOREIGN KEY (article_id) REFERENCES articles(id) ON DELETE CASCADE,
+                FOREIGN KEY (author) REFERENCES users(email) ON DELETE CASCADE,
+                FOREIGN KEY (parent_comment_id) REFERENCES comments(id) ON DELETE CASCADE
+            );
             ");
 
             $columns = $db->query("PRAGMA table_info(comments);")->fetchAll(PDO::FETCH_ASSOC);
@@ -63,6 +66,7 @@ class DatabaseCommentManager implements CommentManagerDAO
 
             $db = new PDO($dsn, null, null);
             $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            $db->exec('PRAGMA foreign_keys = ON;');
 
             return $db;
 
diff --git a/php/model/DatabaseUserManager.php b/php/model/DatabaseUserManager.php
index 7ecf119..311366d 100644
--- a/php/model/DatabaseUserManager.php
+++ b/php/model/DatabaseUserManager.php
@@ -55,6 +55,7 @@ class DatabaseUserManager implements UserManagerDAO {
 
             $db = new PDO($dsn, null, null);
             $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            $db->exec('PRAGMA foreign_keys = ON;');
 
             return $db;