MySQL Error Occurred

Error Message:
1064: 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 'ORDER BY I.productId DESC' at line 1

SQL:
SELECT I.productId FROM CubeCart_inventory AS I LEFT JOIN CubeCart_category AS C ON I.cat_id = C.cat_id WHERE I.disabled='0' AND I.cat_id = ORDER BY I.productId DESC