Question

I have a query like:

SELECT 
    R.*     
FROM 
    (SELECT A, B, 
            (SELECT smth from another table) as C,
     ROW_NUMBER() OVER (ORDER BY C DESC) AS RowNumber 
     FROM SomeTable) R
WHERE 
     RowNumber BETWEEN 10 AND 20

This gives me an error on ORDER BY C DESC.

I understand why this error is caused, so I’ve thought of adding another SELECT with ORDER BY and only than selecting rows from 10 to 20. But I don’t think it’s good to have 3 nested SELECT commands.

How else is it possible to select these rows?

Answer 1

A column cannot refer to an alias on same level, you have to table-derive it first, or use CTE.

SELECT 
    R.* , ROW_NUMBER() OVER (ORDER BY C DESC) AS RowNumber     
FROM 
    (SELECT A, B, (SELECT smth from another table) as C
     FROM SomeTable) R
-- WHERE 
     -- but you still cannot do this
     -- RowNumber BETWEEN 10 AND 20

Need to do this:

select S.*
from
(
    SELECT 
        R.* , ROW_NUMBER() OVER (ORDER BY C DESC) AS RowNumber     
    FROM 
        (SELECT A, B, 
                (SELECT smth from another table) as C
         FROM SomeTable) R
) as s
where s.RowNumber between 10 and 20

To avoid deep nesting and to make it at least look pleasant, use CTE:

with R as
(
     SELECT A, B, (SELECT smth from another table) as C
     FROM SomeTable
)
,S AS 
(
    SELECT R.*, ROW_NUMBER() OVER (ORDER BY C DESC) AS RowNumber
    FROM R
)
SELECT S.*
FROM S
WHERE S.RowNumber BETWEEN 1 AND 20