sql中union 的问题

[canzai]

如下：
表A：
id name date
1 aa 10-15
2 bb 10-14
3 cc 10-12

表B：
name date
aa 10-19
bb 10-13
dd 10-10

如果使用 select name,date from A union select name,date from B 之后就会根据表A的情况（即表A有了就不显示表B的记录）显示如下：
name date
aa 10-15
bb 10-14
cc 10-12
dd 10-10
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
而如何根据date的情况（即，重复的记录留下date大的那条），显示如下：
name date
aa 10-19
bb 10-14
cc 10-12
dd 10-10

[-晴天]

楼主弄错了吧!

create table ta(id int,name varchar(10),date varchar(10))
insert into ta select 1,'aa','10-15'
insert into ta select 2,'bb','10-14'
insert into ta select 3,'cc','10-12'
create table tb(name varchar(10),date varchar(10))
insert into ta select 1,'aa','10-19'
insert into ta select 2,'bb','10-13'
insert into ta select 3,'dd','10-10'

select name,date from ta
union all
select name,date from tb
go
drop table ta,tb
/*
name       date
---------- ----------
aa         10-15
aa         10-19
bb         10-13
bb         10-14
cc         10-12
dd         10-10

*/

[canzai]

自己顶一下

[-晴天]

当然,楼主要的是这个:

create table ta(id int,name varchar(10),date varchar(10))
insert into ta select 1,'aa','10-15'
insert into ta select 2,'bb','10-14'
insert into ta select 3,'cc','10-12'
create table tb(name varchar(10),date varchar(10))
insert into ta select 1,'aa','10-19'
insert into ta select 2,'bb','10-13'
insert into ta select 3,'dd','10-10'

select name,max(date) from (
select name,date from ta
union all
select name,date from tb
)t
group by name
go
drop table ta,tb
/*
name       date
---------- ----------
aa         10-19
bb         10-14
cc         10-12
dd         10-10
*/

[-晴天]

有一点小改动:

create table ta(id int,name varchar(10),date varchar(10))
insert into ta select 1,'aa','10-15'
insert into ta select 2,'bb','10-14'
insert into ta select 3,'cc','10-12'
create table tb(name varchar(10),date varchar(10))
insert into ta select 1,'aa','10-19'
insert into ta select 2,'bb','10-13'
insert into ta select 3,'dd','10-10'

select name,max(date)as date from (
select name,date from ta
union all
select name,date from tb
)t
group by name
go
drop table ta,tb
/*
name       date
---------- ----------
aa         10-19
bb         10-14
cc         10-12
dd         10-10
*/

[canzai]

我在asp中使用怎么不行呀？
能不能写成一句sql=“......"之类的语句？

[-晴天]

可以.

sqlstr="select name,max(date)as date from (select name,date from ta union all select name,date from tb)t group by name"
conn.execute(sqlstr)