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 `si`.`IDLang` = "2" AND `products_sizes`.`status` = 1 ORDER BY `products_si' at line 1
SELECT `products_sizes`.`size`, `si`.`si_unit`, `products_sizes`.`onStock` FROM `products_sizes` INNER JOIN `si` ON (`products_sizes`.`IDSI` = `si`.`IDSI`) WHERE `products_sizes`.`IDProduct` = "" AND `products_sizes`.`IDCatalog` = AND `si`.`IDLang` = "2" AND `products_sizes`.`status` = 1 ORDER BY `products_sizes`.`priority` DESC, `products_sizes`.`size` ASC ;