Question

I retrieve data form 3 tables (date and qty), some data may overlap but is not sure which tables. For example some days may overlap in
tables t1 and t2 but not in t3,
or t2 and t3 but not in t1
or t1 and t3 but not in t2

If I perform a full join I end up with lots of nulls and three different date columns.

How can I get data to format:
date,qty1, qty2, gty3 where [date] would contain all days form 3 tables?
Zero would replace all null values

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