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發表時間：2016/10/13 6:53 |
- Webmaster
- 註冊日: 2008/2/19
- 來自:
- 發表數: 15773
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- [轉貼]USE MULTIPLE LEFT JOIN
- USE MULTIPLE LEFT JOIN
Is it possible to use multiple left join in sql query? if not then whats the solution?
LEFT JOIN
ab
ON
ab.sht = cd.sht
i want to add to atach one more query like this to it? will it work?
LEFT JOIN
ab AND aa
ON
ab.sht = cd.sht
AND
aa.sht = cc.sht
Will this work?
--------------------------------------------------------------------------------
Yes it is possible. You need one ON for each join table.
LEFT JOIN ab
ON ab.sht = cd.sht
LEFT JOIN aa
ON aa.sht = cd.sht
Incidentally my personal formatting preference for complex SQL is described in http://bentilly.blogspot.com/2011/02/sql-formatting-style.html. If you're going to be writing a lot of this, it likely will help.
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Yes, but the syntax is different than what you have
SELECT
<fields>
FROM
<table1>
LEFT JOIN <table2>
ON <criteria for join>
AND <other criteria for join>
LEFT JOIN <table3>
ON <criteria for join>
AND <other criteria for join>
--------------------------------------------------------------------------------
The required SQL will be some like:-
SELECT * FROM cd
LEFT JOIN ab ON ab.sht = cd.sht
LEFT JOIN aa ON aa.sht = cd.sht
....
Hope it helps.
--------------------------------------------------------------------------------
You have two choices, depending on your table order
create table aa (sht int)
create table cc (sht int)
create table cd (sht int)
create table ab (sht int)
-- type 1
select * from cd
inner join cc on cd.sht = cc.sht
LEFT JOIN ab ON ab.sht = cd.sht
LEFT JOIN aa ON aa.sht = cc.sht
-- type 2
select * from cc
inner join cc on cd.sht = cc.sht
LEFT JOIN ab
LEFT JOIN aa
ON aa.sht = ab.sht
ON ab.sht = cd.sht
原文出處：sql - USE MULTIPLE LEFT JOIN - Stack Overflow
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[轉貼]USE MULTIPLE LEFT JOIN (冷日