function i query

Hey..

Jeg har en function som jeg skal have smidt ind i en mysql_query, men jeg aner ikke hvordan...??

eks.

function age($birth)
{
    $year = substr($birth, 0, 4);
    $month = substr($birth, 4, 2);
    $day = substr($birth, 6, 2);
   
    if($month < date(m)) $age = date(Y)-$year;
    elseif($month == date(m) && $day >= date(d)) $age = date(Y)-$year;
    else $age = date(Y)-$year-1;
   
    return $age;
}

SELECT alder AS age(birth) FROM table WHERE alder=20