SQL中join的用法解析（inner join、full out join、left join）

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原文鏈接：https://blog.csdn.net/Megustas_JJC/article/details/86092980

對於各種join情況的總結圖：

例如有如下關系的數據：

1、inner join

 

select * from Table_a
join Table_b on Table_a.id_a = Table_b.id_b

 

2.1、full outer join等於full join

 

select * from Table_a
full join Table_b
on Table_a.id_a = Table_b.id_b

2.2、full outer join but a.Key is null or b.Key is null

 

select * from Table_a
full outer join Table_b
on Table_a.id_a = Table_b.id_b
where Table_a.id_a is null or Table_b.id_b is null

3.1、left outer join等於left join

 

select * from Table_a
left join Table_b on Table_a.id_a = Table_b.id_b

 

3.2、left outer join but b.Key is null

 

select * from Table_a

left outer join Table_b on Table_a.id_a = Table_b.id_b

where Table_b.id_b is null

 

笛卡爾積
select * from Table_a ,Table_b

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版權聲明：本文為CSDN博主「Megustas_JJC」的原創文章，遵循 CC 4.0 BY-SA 版權協議，轉載請附上原文出處鏈接及本聲明。
原文鏈接：https://blog.csdn.net/Megustas_JJC/article/details/86092980