Coupon de réduction

MDB2 Error: syntax error
_doQuery: [Error message: Could not execute statement] [Last executed query: UPDATE t_coupon SET compteur = compteur +1 WHERE id_coupon = ] [Native code: 1064] [Native message: 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 '' at line 3]