如何将以下依赖子查询更改为自连接?
SELECT d.name, d.created,
(SELECT SUM( q1.payout ) FROM client AS q1 WHERE q1.uid = d.uid) AS payout,
(SELECT COUNT( q2.uid ) FROM client AS q2 WHERE q2.uid = d.uid AND q2.winning =1) AS cnt
FROM client AS d group by d.name, d.created ORDER BY cnt DESC LIMIT 0 , 10;
最佳答案
SELECT d.name, d.created, SUM(q1.payout) AS psum, COUNT(q2.uid) AS cnt
FROM client d
LEFT JOIN
client q1
ON q1.uid = d.uid
LEFT JOIN
client q2
ON q2.uid = d.uid
AND q2.winning =1
GROUP BY
d.name, d.created
ORDER BY
cnt DESC
LIMIT 0, 10
如果uid
是一个PRIMARY KEY
,你可以这样重写它:
SELECT d.name, d.created, SUM(payout) AS psum, COUNT(IF(winning = 1, uid, NULL)) AS cnt
FROM client d
GROUP BY
d.name, d.created
ORDER BY
cnt DESC
LIMIT 0, 10
关于mysql - 自连接的依赖子查询,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1306584/