basic question

[jasondavis]

function updatefriendrequest(){ 
	$temp=$_SESSION['info'];
	$sql_friend="select * from friend_friend where  friendid='$temp[auto_id]' and alert_message='yes'";
	$result_friend=executeQuery($sql_friend);
    while($line_friend=mysql_fetch_array($result_friend)){ 
     $sql_friendupdate="update friend_friend set alert_message='no' where  friendid='$temp[auto_id]' and autoid='$line_friend[autoid]'"; 
      executeQuery($sql_friendupdate);
    } 
   $temp='';
}

Here is my funtion above, is it better to do that, it checks to see if there is a record to update or better to do the way below where it just updates it, the way below will try to update it even if it does not exist, is that bad for a high traffic site?

$sql_friendupdate="update friend_friend set alert_message='no' where  friendid='$temp[auto_id]'"; 
      executeQuery($sql_friendupdate);

[TheDefender]

You wouldn't necessarily need to while loop...
Use mysql_num_rows() to se if it finds 1 result from your original query. If it does, then just run your update query. If not, no need to do so... (of course, this all assumes you are using validation to prevent SQL injections)

IMHO, there's no need to arbitrarily update fields in a DB that don't need to be updated, but I can't really give you any explanation to support either case...