error 1064: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'AND reis.hidden=0
         AND reis.ID <> 
          GROUP BY reis.ID
       ...' at line 11 (SELECT 
         reis.*,reis_group.name AS str_reis_group,
          reis_type.name_mod_rewrite AS type_name_mod_rewrite 
         FROM reis 
          LEFT JOIN reis_group ON reis_group.ID = reis.ID_reis_group
          LEFT JOIN reis_type ON reis_type.ID = reis.ID_reis_type 
           LEFT JOIN `schema` ON `schema`.reis_ID = reis.ID
         WHERE 
         `schema`.ID_difficulty = '' 
         AND reis.ID_reis_group =  
         AND reis.hidden=0
         AND reis.ID <> 
          GROUP BY reis.ID
          LIMIT 0,5)