Har problem med att kombinera HAVING med WHERE på en mycket enkel QUERY

Jag har ingen PostgreSQL-bakgrund men vi får se om detta fungerar:

Jag skulle börja detta med att förenkla det genom att skriva en fråga som först returnerar den totala poängen per spelare:

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

Gå nu med datauppsättningen till spelare för att hitta grupperna:

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

Nu har vi alla spelare, deras totala poäng och deras grupp. Vill vi identifiera vinnaren efter grupp? Vi kan använda ranking funktioner för att göra detta:

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

Nu väljer vi bara ut de översta i varje grupp (rank =1) med 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

Ser komplicerat ut? ja, men du kan se att det slutliga resultatet tillhandahålls bit för bit. Varje steg i detta är en "undertabell" och du kan köra och observera data vid varje punkt.