Sql加入部分重叠的数据

Question

我从3个表(日期和数量)检索数据,一些数据可能重叠但不确定哪些表.例如,某些天可能在表t1和t2中重叠但在t3或t2和t3中不重叠但在t1或t1和t3中不重叠但在t2中不重叠

如果我执行完全连接,我最终会得到很多空值和三个不同的日期列.

如何获取要格式化的数据: date,qty1, qty2, gty3哪里[date]将包含3个表的所有日期？零将替换所有空值

07/02/2012  ||   2   ||  0  ||  7 


CREATE TABLE t1 (
    [date] [nvarchar](10) 
    ,qtyt1 [int]
) 

CREATE TABLE t2 (
    [date] [nvarchar](10) 
    ,qtyt2 [int]
) 

CREATE TABLE t3 (
    [date] [nvarchar](10) 
    ,qtyt3 [int]
) 


insert into t1 values ('05/02/2012', 2)
insert into t1 values ('07/02/2012', 3)
insert into t2 values ('06/02/2012', 4)
insert into t2 values ('08/02/2012', 5)
insert into t3 values ('07/02/2012', 7)
insert into t3 values ('08/02/2012', 11)


select * from t1
full join t2 on t1.date = t2.date 
full join t3 on t2.date = t3.date

Answer 1

SELECT COALESCE(t1.date, t2.date, t3.date) AS date,
       qtyt1,
       qtyt2,
       qtyt3
FROM   t1
       FULL JOIN t2
         ON t1.date = t2.date
       FULL JOIN t3
         ON ISNULL(t2.date, t1.date) = t3.date