Můžete také vložit součet do příkazu case, kde případ vyhodnocuje druhou podmínku, a pak sečíst pouze ty záznamy, kde je podmínka pravdivá...
SELECT m.member_id, m.teamname,
Sum(Case When r.track_Id = '$chosentrack'
Then total_points Else 0 End) TotalChosenTrackPoints,
Sum(Case When r.track_Id < '$chosentrack'
Then total_points Else 0 End) TotalLessThanChosenTrackPoints,
total_points as last_race_points
FROM members m
Join members_leagues l
On l.member_id = m.member_id
Join member_results r
On r.member_id = m.member_id
Where l.league_id = '$chosenleague'
And l.start_race = '$chosentrack'
Group By m.member_id
Order By r.total_points Desc,
last_race_points Desc, m.TeamName Desc