内链接--取共有部分

select <select_list>

from tableA a

inner join tableB b

on a.key =b.key

 ab共有加a的独有（全a）--左链接

select<select_list>

from tableA a

left join tableB b

on a.key=b.key 

b独有+ab共有(全b)

select<select_list>

from tableA a

right join tableB b

on a.key=b.key

select<select_list>

frin tableA a

left join tableB b

on a.key =b.key

where b.key is null

select<select_list>

from tableA a

right join tableB b

on a.key=b.key

where a.key is null

select<select_list>

from tableA a

full outer join tableB b

on a.key=b.key

select<select_list>

from tableA a

full outer join tableB b

on a.key=b.key

where a.key is null

or b.key is null

作者：三号小玩家