No se pudo ejecutar la consulta

SELECT id,filetitle,filesize,filename,description,screenurl,submitdate FROM mos_downloads WHERE catid =  AND folderid = 0

Error MySQL: : 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 folderid = 0' at line 1

Este Script no puede continuar.