MySQL Query Error select id,title,subtitle,class from dx_kskm_news where class='参考书' and ejxk_id in ('080600','080603','080652','080601','080602','080654','080655','080651','080653','0806J4') 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