MySQL Query Error select id,title,subtitle,class from dx_kskm_news where class='参考书' and ejxk_id in ('050302','050300','050301','050353','050355','050360','050372','050365','050369','050371','050352','050351','050356','050370','050358','050359','050366','050373','050374','050375','050361','050362','050363','050367','050368','050354','050364','050382','050381','0503J4','050383','050385','050384','50301','50300','50302','0503J7','0503Z7') 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