Mysql 多个on和join
我学到了,我可以重写这样的查询Mysql 多个on和join,mysql,join,Mysql,Join,我学到了,我可以重写这样的查询 SELECT d FROM tbl1 WHERE a in ( SELECT b FROM tbl2 WHERE c = "Something" ) 进入我认为更快的查询: SELECT d FROM tbl1 LEFT JOIN tbl2 ON tbl1.a = tbl2.b WHERE tbl2.c = "Something" 但我有一个问题需要重写以下查询: SELECT name, nick FROM cu WHERE uid
SELECT d
FROM tbl1
WHERE a in (
SELECT b
FROM tbl2
WHERE c = "Something"
)
进入我认为更快的查询:
SELECT d
FROM tbl1 LEFT JOIN tbl2
ON tbl1.a = tbl2.b
WHERE tbl2.c = "Something"
但我有一个问题需要重写以下查询:
SELECT name, nick
FROM cu
WHERE uid IN (
SELECT friend
FROM cf
WHERE user IN (
SELECT uid
FROM cu
WHERE sid = "abc"
)
)
编辑:
刚刚找到它:这应该是等效的:
select cu.*
from cu join
cf
on cu.uid = cf.friend join
cu cu2
on cu2.uid = cf.user
where cu2.sid = 'abc';
请注意,此操作只需要内部联接。这应该是等效的:
select cu.*
from cu join
cf
on cu.uid = cf.friend join
cu cu2
on cu2.uid = cf.user
where cu2.sid = 'abc';
请注意,这只需要内部联接。刚刚找到解决方案。无论如何,谢谢你的快速回答:@Cubinator73。并排查看这两种解决方案有助于更好地理解不同的做事方式。祝你学习SQL好运。刚刚找到解决方案。无论如何,谢谢你的快速回答:@Cubinator73。并排查看这两种解决方案有助于更好地理解不同的做事方式。祝你学习SQL好运。