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

 

(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