老是出现mysql_fetch_array():suppliedargumentisnotavalidMySQLresultresource

总是出现mysql_fetch_array(): supplied argument is not a valid MySQL result resource
总是出现mysql_fetch_array(): supplied argument is not a valid MySQL result resource in D:\的错误。请各位帮帮忙！

$sql = "select * from `topic` order by id limit $start, $each_page";
mysql_query("set names 'gbk'");
$result = mysql_query($sql);
while (@$row=mysql_fetch_array($result))

------解决方案--------------------
查询失败！
$sql = "select * from `topic` order by id limit $start, $each_page";
$start 和 $each_page 至少有一个不存在或值非法