no data in field errors, die() not helpn

[Anon]

I get this error:
Warning: Unable to jump to row 0 on MySQL result index 2

when the data doesn't exist in the query:
$result = mysql_query($sql) or die("Couldn't execute query.");

if ($filename = mysql_result($result,0, "filename") ){
echo "$filename";
}

The query works, and so it doesn't die, but the mysql_result(); is null, so how do I get around this?

[[deleted]]

By checking wether there were any results in the first place:

if (mysql_num_rows($result)==0)
{
// no results
}
else
{
// process results
}