Question

Please refer the below script

    declare @table1 table
    (
    col1 int
    )

    declare @table2 table
    (
    col2 int
    )

    insert into @table1 values(1)
    insert into @table1 values(2)
    insert into @table1 values(3)
    insert into @table1 values(5)
    insert into @table1 values(7)

    insert into @table2 values(1)
    insert into @table2 values(3)
    insert into @table2 values(3)
    insert into @table2 values(6)
    insert into @table2 values(4)
    insert into @table2 values(7)

Case 1:

select * from @table1 a left outer join @table2 b on a.col1=b.col2
    order by col1 

Result 1:

         col1       col2        
     -----------  ----------- 
    |    1       |    1       |
    |    2       |    NULL    |
    |    3       |    3       |
    |    3       |    3       |
    |    5       |    NULL    |
    |    7       |    7       |
    ---------------------------

Case 2:

select * from @table1 a right outer join @table2 b on a.col1=b.col2
    order by col2 

Result 2:

         col1             col2        
     -----------  ----------- 
    |    1       |    1       |
    |    3       |    3       |
    |    3       |    3       |
    |    NULL    |    4       |
    |    NULL    |    6       |
    |    7       |    7       |
    ---------------------------

Actual Case:

select * from @table1 a full outer join @table2 b on a.col1=b.col2

Actual Result:

         col1        col2        
     -----------  ----------- 
    |    1       |    1       |
    |    2       |    NULL    |
    |    3       |    3       |
    |    3       |    3       |
    |    5       |    NULL    |
    |    7       |    7       |
    |    NULL    |    6       |
    |    NULL    |    4       |
    ---------------------------

Expected Result:

         col1        col2        
     -----------  ----------- 
    |    1       |    1       |
    |    2       |    NULL    |
    |    3       |    3       |
    |    3       |    3       |
    |    NULL    |    4       |
    |    5       |    NULL    |
    |    NULL    |    6       |
    |    7       |    7       |
    ---------------------------

I tried union all with left and right join query but it doubles the result set. Is there a way that I can get this expected output.

Thanks,
Esen.

Answer 1

You can use

SELECT *
FROM   @table1 a
       FULL OUTER JOIN @table2 b
         ON a.col1 = b.col2
ORDER  BY Isnull(col1, col2) 

to get your desired order. Without an ORDER BY no ordering is guaranteed.