create table A(sfzno varchar(18), yjny varchar(6))
insert into a values('XXXX' , '200801')
insert into a values('XXXX' , '200802')
insert into a values('XXXX' , '200803')
insert into a values('DDDD' , '200801')
create table b(sfzno varchar(18), sjny varchar(6),je int)
insert into b values('XXXX', '200801' , 100 )
insert into b values('XXXX', '200803' , 50)
insert into b values('DDDD', '200801' , 120)
insert into b values('DDDD', '200802' , 70 )
go
select a.sfzno,a.yjny,b.sjny,b.je
from a left join b
on a.sfzno = b.sfzno and a.yjny = b.sjny
order by a.sfzno,a.yjny
drop table a , b
/*
sfzno yjny sjny je
------------------ ------ ------ -----------
DDDD 200801 200801 120
XXXX 200801 200801 100
XXXX 200802 NULL NULL
XXXX 200803 200803 50
（所影响的行数为 4 行）
*/
