什么'；我的代码有问题吗?mysql_num_rows(）要求参数1为resource

What's wrong with my code? mysql_num_rows() expects parameter 1 to be resource

$sql="SET @rank=0; SELECT * FROM (SELECT *, @rank:=@rank+1 AS Rank FROM scoregame where userid=33 order by score DESC) AS t";
$query=mysql_query($sql);
if(mysql_num_rows($query) != "")
{
  $stt=1;
  while($row=mysql_fetch_array($query))
  {
    $stt++;
    echo $row['score'];
  }
}

 Warning: mysql_num_rows() expects parameter 1 to be resource

您尝试同时运行两个查询。这个PHP函数不起作用。但您可以将其简化为一个查询

SELECT *, @rank:=@rank+1 AS Rank 
FROM scoregame 
cross join (select @rank := 0) r
where userid=33 
order by score DESC