inner join、 left join、 right join

declare @a as table
(
 FID   int,
 FName varchar(10)
)

declare @b as table
(
 FID   int,
 FName varchar(10)
)

insert into @a(FID,FName)
values
(1,'1-A'),
(2,'2-A'),
(2,'2-AA'),
(3,'3-A'),
(4,'4-A'),
(5,'5-A'),
(5,'5-AA')

insert into @b(FID,FName)
values
(2,'2-B'),
(4,'4-B'),
(4,'4-BB'),
(5,'5-B'),
(5,'5-BB'),
(6,'6-B'),
(7,'7-B')

select * from @a 

select * from @b

  

select a.*, 'inner join' as FType,  b.*
from @a a
inner join @b b on b.FID=a.FID ;

  

select a.*, 'left join' as FType, b.*
from @a a
left join @b b on b.FID=a.FID 

  

select a.*, 'right join' as FType, b.*
from @a a
right join @b b on b.FID=a.FID