Question

I have a SQL statement which is being used to page the results using ROW_NUMBER()

SELECT * FROM (
    SELECT
        ROW_NUMBER() OVER ( ORDER BY [tbl1].[Col1] ASC ) As RowNumber,
        [tbl1].[Col1],
        [tbl1].[Col2],
        [tbl1].[Col3],
        ( SELECT [tbl2].[Col1] 
          FROM [tbl2] 
          WHERE [tbl2].[id] = [tbl1].[id] 
                AND [tbl2].[subid] = 2 ) As theColumnName
    FROM
        [tbl1]
) As tbl
WHERE RowNumber BETWEEN 1 AND 10

This all works fine and as expected. However I now want to introduce some additional ORDER BY functionality based on a value passed into the stored procedure.

So I have updated my ROW_NUMBER() OVER (ORDER BY... statement to

ROW_NUMBER() OVER (ORDER BY 
    CASE WHEN @sortBy = 'type1' THEN [tbl1].[Col1]
         WHEN @sortBy = 'type2' THEN [tbl1].[Col2]
    END,
    CASE WHEN @sortBy = 'type3' THEN [tbl1].[Col3]
    END
ASC) As RowNumber

As you can see here I have a CASE statement within the OVER () method, and there are two CASE‘s because [Col3] is a different data type than the other colums.

Now this works fine, but I cannot find out how to order by my column theColumnName as I just receive the error message Invalid column name 'theColumnName'.

WHEN @sortBy = 'type4' THEN theColumnName

I have even tried to use the column number, e.g. WHEN @sortBy = 'type4' THEN 5 but this will not work either.

Is there a way to Order By this custom column name?

Answer 1

You need to move the subquery to the from clause, such as:

SELECT
    ROW_NUMBER() OVER ( ORDER BY [tbl1].[Col1] ASC ) As RowNumber,
    [tbl1].[Col1],
    [tbl1].[Col2],
    [tbl1].[Col3],
    t2.col1 As theColumnName
FROM [tbl1] t join
     (select id, col1
      from tbl2
      where subid = 2
    ) t2
    on t.id = t2.id

Now, you will be able to include t2.col1 in the row_number() order by clause.