如何优化具有左硬连接的查询？

Question

我有一个查询

SELECT 
"athlete"."id" AS "athlete_id" 
FROM "athlete" 
LEFT JOIN "athlete_in_game" ON athlete.id = athlete_in_game.id_athlete 
LEFT JOIN "athlete_in_team" ON athlete.id = athlete_in_team.id_athlete 
LEFT JOIN "game" ON 
    athlete_in_team.id_team = game.id_team_home OR 
    athlete_in_team.id_team = game.id_team_away OR 
    athlete_in_game.id_game = game.id 
LEFT JOIN "sport_competition" ON sport_competition.id_game = game.id 
GROUP BY "athlete"."id" 

我需要选择其在比赛中发挥所有的运动员。但可能是因为几场比赛没有数据在表格“运动员在线游戏”中，并且在这种情况下，我会从表“athlete_in_team”中的所有运动员参加这些游戏。正因为如此，我在第三个左连接中使用双“OR”。我需要所有书面条件，但由于双“或”，它可能会工作太久。无论如何，是否有机会优化它？

Answer 1

我认为首先你必须首先改善模式。团队相关信息应该是单独的表格。和游戏应该是分开的。你不需要和我想的game表左边加入。只有加入athlete_in_game和athlete_in_team就足够了。像这样

SELECT 
"athlete"."id" AS "athlete_id" 
FROM "athlete" 
LEFT JOIN "athlete_in_game" ON athlete.id = athlete_in_game.id_athlete 
LEFT JOIN "athlete_in_team" ON athlete.id = athlete_in_team.id_athlete 
JOIN "game" ON 
    athlete_in_team.id_team = game.id_team_home OR 
    athlete_in_team.id_team = game.id_team_away OR 
    athlete_in_game.id_game = game.id 
LEFT JOIN "sport_competition" ON sport_competition.id_game = game.id 
GROUP BY "athlete"."id"