Warning: mysql_fetch_row(): supplied argument is not a valid MySQL result resource

今天在用php写数据连接时出现了错误，提示Warning: mysql_fetch_row(): supplied argument is not a valid MySQL result resource

原因：

<?php
        $result=mysql_query("select  * from kcb limit ".(($page_curr-1)*3).",3");
        while($row =mysql_fetch_row($result)) {
    ?>

$sql="select * from emp limit(这里需要空格)".($pagenow-1)*$pagesize.",$pagesize";