Sql Jions 的简易理解

Select  * from TableA A  left jion TableB  B on  A.key = B.key

 

Select  * from TableA A  right jion TableB  B on  A.key = B.key

Select  * from TableA A inner jion TableB  B on  A.key = B.key

Select  * from TableA A left jion TableB  B on  A.key = B.key where B.key is NULL

Select  * from TableA A right jion TableB  B on  A.key = B.key where A.key is NULL

Select  * from TableA A full outer jion TableB  B on  A.key = B.key

Select  * from TableA A full outer jion TableB  B on  A.key = B.key  where A.key is NULL or B.key is NULL