请教大家个问题:数据库 中有 a表
sysno qty
0001 100
0002 200
0003 300b表有
sysno qty
0001 50怎么在连表查询的时候出来
sysno a.qty b.qty
0001 100 50
0002 200 0
0003 300 0 先谢谢各位了
sysno qty
0001 100
0002 200
0003 300b表有
sysno qty
0001 50怎么在连表查询的时候出来
sysno a.qty b.qty
0001 100 50
0002 200 0
0003 300 0 先谢谢各位了
insert into a values('0001', 100)
insert into a values('0002', 200)
insert into a values('0003', 300)create table b(sysno varchar(10),qty int)
insert into b values('0001', 50)select a.* , isnull(b.qty,0) b_qty from a left join b on a.sysno = b.sysno
drop table a , b/*
sysno qty b_qty
---------- ----------- -----------
0001 100 50
0002 200 0
0003 300 0(所影响的行数为 3 行)
*/
from a
left join b
on a.sysno = b.sysno
from a left join b
on a.sysno = b.sysno