select isnull(isnull(a.time,b.time),c.time) as time,
a.data,b.data,c.data
from a
full join b on a.time=b.time
full join c on a.time=c.time or b.time=c.time
order by 1

/**
time  data        data        data
----- ----------- ----------- -----------
07:59 NULL        1           NULL
08:59 12          NULL        23
09:00 13          2           NULL
10:01 15          NULL        NULL
11:00 NULL        3           25
12:00 NULL        NULL        26

(6 行受影响)
**/

 只有索引了
CREATE INDEX time_index ON A(time)
CREATE INDEX time_index ON B(time)
CREATE INDEX time_index ON C(time)

------解决方案--------------------
2000数据库不能用with的

探讨

回2楼，之前一个贴你我看你回复了，我运行的时候报with 语法错误，我用的是sql2000 是不是这个原因？


------解决方案--------------------

SQL code

--创建一个索引视图
create view v1
as
select time from a
union
select time from b
union
select time from c
go

--按视图查询
select t.time,a.data as A_data,b.data as B_data,c.data as C_data
from v1 t left join a on t.time = a.time
           left join b on t.time = b.time
           left join c on t.time = c.time

------解决方案--------------------
SQL code
SELECT TIME ,SUM(A_DATA) AS A_DATA
   ,SUM(B_DATA) AS B_DATA
   ,SUM(C_DATA) AS C_DATA
FROM (
SELECT TIME ,DATA AS A_DATA,CAST(NULL AS INT) AS B_DATA,CAST(NULL AS INT) AS C_DATA
FROM A
UNION ALL
SELECT TIME ,NULL AS A_DATA,DATA AS B_DATA,CAST(NULL AS INT) AS C_DATA
FROM B
UNION ALL
SELECT TIME ,NULL AS A_DATA,NULL AS B_DATA,DATA AS C_DATA
FROM C
) AS T
GROUP BY TIME

------解决方案--------------------
 那用with表达式也是一样的吧

------解决方案--------------------
你的是用2000的只有用view来做了  

探讨

引用:

SQL code

--创建一个索引视图
create view v1
as
select time from a
union
select time from b
union
select time from c
go

--按视图查询
select t.time,a.data as A_data,b.data as B_……