MySQL Query Error, sql: SELECT aid,mid,subject,date_format(tm,'%Y.%m.%d') as tm,pic,date_format(`declare`,'%Y/%m/%d') as `declare`,date_format(`deadline`,'%Y/%m/%d') as `deadline`,datediff(deadline, CURRENT_DATE) as days,datediff(`declare`, CURRENT_DATE) as days_end,pic_path,zhuban_company,changguan FROM exhibit where flag=1 and subject like '%%E5%AE%B6%E5%85%B7%' ORDER BY `tm` DESC LIMIT -20 , 20, ErrMsg: 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 '-20 , 20' at line 1