How to do pagination based on a calculated column - sql-server

Question

I have a problem ascribable to this simplified version:
I have a table in Sql Server 2008 like this (it's a denormalized table specific for my search):
ItemId | CategoryId | Descr | ExtendedDescription
0001 | 1 | Mouse X | Blue mouse
0002 | 1 | Blue Pen | Beautiful ....
0003 | 2 | Blue Pencil | Pencil with ...
0004 | 2 | Eraser | Eraser with ....
I need to search a word (like "Blue") in this table, assign a rank to the result based on where the word appears and group the result by CategoryId summing the rank.
I am able to do that; the problem arises when I try to paginating the result.
This is the stored procedure that I tried (now the word to search is fixed, but I know how to make it a parameter; I know also how to filter ID to have pagination):
CREATE PROCEDURE [dbo].[spSearch]
AS
BEGIN
SET NOCOUNT ON;
SELECT
[CategoryId],
SUM(
CASE WHEN (PATINDEX('%Blue%', Descr) > 0) THEN 100 ELSE 0 END +
CASE WHEN (PATINDEX('%Blue%', ExtendedDescription) > 0) THEN 10 ELSE 0 END
) AS Ranking,
ROW_NUMBER() OVER(ORDER BY CategoryId DESC) ID
FROM [dbo].[Data]
where (Descr like '%Blue%' or
ExtendedDescription like '%Blue%')
GROUP BY CategoryId
ORDER BY Ranking DESC
END
With this sp I get the following result:
CategoryId | Ranking | ID
0001 | 110 | 2
0002 | 100 | 1
The problem is: to paginating the result, I need that ID (ROW_NUMBER) is generated ordering descending the Ranking, while in this way it's generated in the order of CategoryId.
If I try to change the sp in this way:
ROW_NUMBER() OVER(ORDER BY Ranking DESC) ID
I can't save the sp because Ranking is not a column.
Do you have some hint?

Answer 1

I think by using Common Table expression (CTE) we can solve this
Try this
;WITH cte AS
(
SELECT
[CategoryId],
SUM(
CASE WHEN (PATINDEX('%Blue%', Descr) > 0) THEN 100 ELSE 0 END +
CASE WHEN (PATINDEX('%Blue%', ExtendedDescription) > 0) THEN 10 ELSE 0 END
) AS Ranking,
ROW_NUMBER() OVER(ORDER BY CategoryId DESC) ID
FROM [dbo].[Data]
where (Descr like '%Blue%' or
ExtendedDescription like '%Blue%')
GROUP BY CategoryId
)
SELECT ROW_NUMBER () OVER(ORDER BY Ranking DESC) AS r_no,
Ranking,
ID
FROM cte