两张表合并问题，

[EANFS]

两张表的结构相同，
Ａ表，Ｂ表
对Ｂ表进行修改与新增的动作后，将Ｂ表的数据更新到Ａ表中，

Ａ　　　　　　　　　　　　　　　　　　Ｂ
userid username userid username
1 a 1 a
2 b 2 c
3 d
结果：

Ａ　
userid username
1 a
2 c
3 d

B不变

[xiaodong_1567]

truncate table A
insert into A
select userid,username from B

[vivianfdlpw]

create trigger tr
on B
for insert,delete,update
as


delete A
from A
join deleted D on A.userid=D.userid

insert A
select * from inserted I
where not exists(select 1
from A
where userid=I.userid
and username=I.username)

[子陌红尘]

update A set username=B.username from A,B where A.userid=B.userid

insert into A select * from B where not exists(select 1 from A where id=B.id)

[EANFS]

谢谢