今天看mysql視訊，裡邊老師給總結了一下七種join語句，感覺挺好的。分享一下

select * from TableA a inner join TableB b on a.id =b.aid

select * from TableA a left join TableB b on a.id =b.aid

select * from TableA a right join TableB b on a.id =b.aid

select * from TableA a left join TableB b where b.aid is null
 

selet * from TableA a right join TableB b on a.id =b.aid where a.id is null

select * from TableA a left join TableB b on a.id =b.aid
union
select * from TableA a right join TableB b on a.id =b.aid

select * from TableA a left join TableB b where b.aid is null
union
select * from TableA a right join TableB b where a.id is null