SQL JOIN

今天在csdn上看到一篇报道,关于如何甄别面试者的一些技巧,发现了几个知识点,总结了一下

SQL JOIN

 

(1)select *from talbeA as  a left join tableB as b  on a.key=b.key

(2)select *from talbeA as  a left join tableB as b  on a.key=b.key where b.key is null
(3) select *from talbeA as  a inner join tableB as b  on a.key=b.key
(4)select *from talbeA as  a right join tableB as b  on a.key=b.key 
(5)select *from talbeA as  a right join tableB as b  on a.key=b.key   where a.key is null
(6)select *from talbeA as  a outer join tableB as b  on a.key=b.key 
(7)select *from talbeA as  a outer join tableB as b  on a.key=b.key where a.key is null and b.key is null

  

 

SQL JOIN

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