Question

以下MySQL语句需要很长时间才能执行，我想因为我正在使用 gameId IN 。

我认为最有效的方法是使用 INNER JOIN ，但我是MySQL的新手，我无法想出 INNER JOIN 语句。你能帮帮我吗？如果有一种比 INNER JOIN 更有效的方式，我想使用它，我只是不确定是否存在。

需要提高效率的声明：

SELECT championId
FROM match_up WHERE
gameId IN
(
    SELECT gameId
    FROM match_up 
    GROUP BY gameId
    HAVING SUM(championId IN (19, 23, 40) AND win = 1) = 3
    AND SUM(championId IN (7, 18) AND win = 0) = 2
)

提前感谢您的帮助和知识！

Answer 1

像

这样的东西

SELECT m.championId
FROM match_up m INNER JOIN
(
    SELECT gameId
    FROM match_up 
    GROUP BY gameId
    HAVING SUM(championId IN (19, 23, 40) AND win = 1) = 3
    AND SUM(championId IN (7, 18) AND win = 0) = 2
) s ON m.gameID = s.gameID

查看Row Subqueries和Subqueries in the FROM Clause

之间的区别

Answer 2

这是一个可能在match_up(gameId, win, championId)上使用索引执行will的方法：

select *
from match_up m
where 3 = (select count(*)
           from match_up m2
           where m2.gameId = m.gameId and
                 m2.championId IN (19, 23, 40) and
                 m2.win = 1
          ) and
      2 = (select count(*)
           from match_up m2
           where m2.gameId = m.gameId and
                 m2.championId IN (7, 18) and
                 m2.win = 0
          );

MySQL：INNER JOIN在本声明中是否最有效？

2 个答案: