Using ranking-function derived column in where clause (SQL Server 2008)

Question

Hoping this is trivial for a SQL-Ninja... Been trying to get the following query working:

This is for SQL Server 2008

SELECT 
    ROW_NUMBER() OVER (ORDER BY Date_Time DESC) AS RowNumber, *
FROM
    (SELECT 
         T.A_ID, T.User_Name, T.Date_Time, T.Value,
         U.ID, U.Name, U.Field1, U.Field2,
         COUNT(U.ID) OVER () AS TotalRows
     FROM 
        TeeTable as T 
    INNER JOIN 
        YouTable AS U ON T.U_ID = U.ID
    WHERE 
        T.Value BETWEEN 222 AND 225) Filtered
WHERE 
    RowNumber BETWEEN 1 AND 5

The values are somewhat contrived to give a specific example, but the spirit of the query is completely preserved. The error I get from this statement is:

Invalid column name 'RowNumber'.

If I remove the final WHERE clause (RowNumber BETWEEN ...) it returns an expected result set (A_ID, User_Name, Date_Time etc...), with RowNumber as a column (with sensical values) in said results. Yet I cannot compare against it in the WHERE clause. I'm clearly doing something stupid but this hits my SQL limit!

I've tried re-arranging this as a CTE as well, (WITH Filtered AS ...) but the end result is the same, it appears that's just a sugar for what I'm already doing anyway.

Ideas? How can I filter against the RowNumber derived column?

Answer 1

You must move the WHERE operator above the project list where RowNumber column is created. Use a derived table or a CTE:

SELECT * 
  FROM (
   SELECT *, ROW_NUMBER() OVER (...) as RowNumber
   FROM ...) As ...
 WHERE RowNumber = ...

the equivalent CTE is:

WITH cte AS (
SELECT *, ROW_NUMBER() OVER (...) as RowNumber
       FROM ...)
SELECT * FROM cte 
WHERE RowNumber = ...   

Answer 2

The Window Functions (of which ROW_NUMBER is the best know) are filled in very late in the query, well after the WHERE clause. Therefore you have to nest it too, in order to filter on it:

SELECT *
FROM (
    SELECT ROW_NUMBER() OVER (ORDER BY Date_Time DESC) AS RowNumber, *
    FROM
    ( SELECT T.A_ID, T.User_Name, T.Date_Time, T.Value,
             U.ID, U.Name, U.Field1, U.Field2,
             COUNT(U.ID) OVER () AS TotalRows
      FROM 
        TeeTable as T INNER JOIN YouTable AS U
        ON T.U_ID = U.ID
        WHERE T.Value BETWEEN 222 AND 225
    ) Numbered
)  Filtered
WHERE RowNumber BETWEEN 1 AND 5

You can also put them in CTE's or Views to get the same effect.

Answer 3

The Problem with the Query comes in because of the the fault in the Logical processing order. This is the logical processing order specified in MSDN dev Network.

Logical Processing Order of the SELECT statement The following steps show the logical processing order, or binding order, for a SELECT statement. This order determines when the objects defined in one step are made available to the clauses in subsequent steps. For example, if the query processor can bind to (access) the tables or views defined in the FROM clause, these objects and their columns are made available to all subsequent steps. Conversely, because the SELECT clause is step 8, any column aliases or derived columns defined in that clause cannot be referenced by preceding clauses. However, they can be referenced by subsequent clauses such as the ORDER BY clause. Note that the actual physical execution of the statement is determined by the query processor and the order may vary from this list. FROM ON JOIN WHERE GROUP BY WITH CUBE or WITH ROLLUP HAVING SELECT DISTINCT ORDER BY TOP

So introduce the ranking function as an alias in the subquery in the from section and then you will be able to set a condition on the alias in the where section.

Good Luck..!!