Mam problemy z połączeniem HAVING z WHERE na bardzo prostym QUERY

Nie mam żadnego tła PostgreSQL, ale zobaczmy, czy to działa:

Zacząłbym to od uproszczenia, pisząc zapytanie, które najpierw zwraca całkowity wynik gracza:

SELECT player_id, SUM(score) score
FROM (
  SELECT first_player as player_id, first_score as score
  FROM matches
  UNION ALL
  SELECT second_player, second_score
  FROM matches
)
GROUP BY player_id

Teraz dołącz ten zbiór danych do graczy, aby znaleźć grupy:

SELECT w.player_id, p.group_id, w.score
FROM
(
  SELECT player_id, SUM(score) score
  FROM (
    SELECT first_player as player_id, first_score as score
    FROM matches
    UNION ALL
    SELECT second_player, second_score
    FROM matches
  )
  GROUP BY player_id
) as w
inner join players p
on p.player_id = w.player_id

Teraz mamy wszystkich graczy, ich łączny wynik i ich grupę. Chcemy zidentyfikować zwycięzcę według grupy? Możemy użyć rankingu funkcje do tego:

SELECT 
w.player_id, 
p.group_id, 
w.score, 
RANK() OVER (PARTITION BY p.group_id ORDER BY score DESC) as group_placement
FROM
(
  SELECT player_id, SUM(score) score
  FROM (
    SELECT first_player as player_id, first_score as score
    FROM matches
    UNION ALL
    SELECT second_player, second_score
    FROM matches
  )
  GROUP BY player_id
) as w
inner join players p
on p.player_id = w.player_id

Teraz po prostu wybieramy najlepsze w każdej grupie (ranga =1) za pomocą WHERE

  SELECT 
  player_id, 
  group_id
  FROM
  (
      SELECT 
      w.player_id, 
      p.group_id, 
      w.score, 
      RANK() OVER (PARTITION BY p.group_id ORDER BY score DESC) as group_placement
      FROM
      (
        SELECT player_id, SUM(score) score
        FROM (
          SELECT first_player as player_id, first_score as score
          FROM matches
          UNION ALL
          SELECT second_player, second_score
          FROM matches
        )
        GROUP BY player_id
      ) as w
      inner join players p
      on p.player_id = w.player_id
    ) as gp
    WHERE group_placement = 1

Wygląda na skomplikowaną? tak, ale widać, że końcowy wynik jest dostarczany po trochu. Każdy krok to „podtablica” i możesz uruchamiać i obserwować dane w każdym punkcie.