SQLserver:declare @a table(a int,b int) declare @b table(a int,b int) insert @a values(1,1) insert @a values(2,2) insert @b values(1,1) insert @b values(3,3)--左: select * from @a Aa left join @b Bb on Aa.a=Bb.a --右: select * from @a Aa right join @b Bb on Aa.a=Bb.a --内 select * from @a Aa join @b Bb on Aa.a=Bb.a --外 select * from @a Aa left full join @b Bb on Aa.a=Bb.a
declare @b table(a int,b int)
insert @a values(1,1)
insert @a values(2,2)
insert @b values(1,1)
insert @b values(3,3)--左:
select * from @a Aa left join @b Bb on Aa.a=Bb.a
--右:
select * from @a Aa right join @b Bb on Aa.a=Bb.a
--内
select * from @a Aa join @b Bb on Aa.a=Bb.a
--外
select * from @a Aa left full join @b Bb on Aa.a=Bb.a
多表联合是要看具體的業務