MySQL Query Error select id,title,subtitle,class from dx_kskm_news where class='参考书' and ejxk_id in ('080300','080355','080354','080360','080352','080358','080356','080351','080359','80300') order by kskm desc limit -50,50 Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in D:\wwwroot\dddjyky\wwwroot\lanmu2.php on line 330