more sql tests

backend/src/routes/challenges.js

@@ -16,9 +16,9 @@ router.get('/', authMiddleware, async (req, res) => {
       FROM challenges c
       INNER JOIN users u ON c.created_by = u.id
       LEFT JOIN challenge_participants cp ON cp.challenge_id = c.id AND cp.user_id = ?
-      WHERE c.created_by = ? OR cp.user_id = ?
+      WHERE c.created_by = ? OR cp.user_id IS NOT NULL
       ORDER BY c.created_at DESC`,
-      [req.user.userId, req.user.userId, req.user.userId, req.user.userId]
+      [req.user.userId, req.user.userId, req.user.userId]
     );
 
     res.json({ challenges });