MySQL子查詢優化

Question

我有一個運行非常慢的查詢：

SELECT * 
FROM games
WHERE games.platform =13
AND games.id NOT 
IN (SELECT game_id
FROM collections
WHERE collections.user_id =1)

我試圖將其重寫為左連接，但返回0個結果：

SELECT * 
FROM games 
LEFT JOIN collections ON collections.game_id = games.id 
WHERE collections.game_id IS NULL AND collections.user_id = 1 AND games.platform = 13
ORDER BY games.name ASC

有人可以在這里指出我的錯誤嗎？

Answer 1

SELECT games.* 
FROM   games 
       LEFT JOIN collections 
         ON collections.user_id = 1 
            AND collections.game_id = games.id 
WHERE  games.platform = 13 
       AND collections.game_id IS NULL 
ORDER  BY games.name ASC 

你需要索引

• （games.id，平台，名稱）
• （collections.user_id，collections.game_id）