select max(id)问题？

(1)字段名下标返回
$sql=”SELECT max(id) as tid FROM asd “;
$result=mysql_query($sql,$db);
$rst=mysql_fetch_array($result);
$valx=$rst[tid];

(2)数字索引下标返回
$sql=”SELECT max(id) FROM asd “;
$result=mysql_query($sql,$db);
$rst=mysql_fetch_row($result);
$valx=$rst[0];

(3)对象返回
$sql=”SELECT max(id) as tid FROM asd “;
$result=mysql_query($sql,$db);
$rst=mysql_fetch_object($result);
$valx=$rst->tid;

$sql=”SELECT max(id) FROM asd “;
$quoteresult=mysql_query($qsql,$db);
if ($row = mysql_fetch_array($quoteresult))
{
$id =$row[“max(id)”];
}