Discuz! info: MySQL Query Error

Time: 2010-9-3 8:21pm
Script: /forumdisplay.php

SQL: select tid,subject , lastpost ,author,authorid,closed from [Table]threads t where fid = 20 order by lastpost desc limit ;
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.