Discuz! info: MySQL Query Error

Time: 2010-7-29 11:49pm
Script: /index.php

SQL: select upid,cid from class where cid=
Error: 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 1
Errno.: 1064

Similar error report has beed dispatched to administrator before.