You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'and cat2.idc=cat1.id and cat2.idg=groups1.id' at line 1
SELECT cat1.name, groups1.name, groups1.id, cat1.id, groups1.coding, cat1.coding FROM cat1, cat2, groups1 where cat2.id= and cat2.idc=cat1.id and cat2.idg=groups1.id;