mysql记录中当前行号

mysql记录中当前行号 
$exec=mysql_query("Select articleid,(@rowNum:=@rowNum+1) as rowNo From product, 
(Select (@rowNum :=0) ) b where bigclassid='$r_bigclassid' Order by product.product_id"); 
$rows=mysql_num_rows($exec); 
$rs=mysql_fetch_array($exec); 

do { 
if($rs['articleid']==$articleid) 
{ 
$inum=$rs['rowNo']; 
} 
} 
while ($rs = @mysql_fetch_array($exec)); 
$current_num=$inum-1;