SQL Row_Number() function in Where Clause

Question

I found one question answered with the Row_Number() function in the where clause. When I tried one query, I was getting the following error:

Answer 1

Using CTE (SQL Server 2005+):

WITH employee_rows AS (
  SELECT t.employee_id,
         ROW_NUMBER() OVER ( ORDER BY t.employee_id ) 'rownum'
    FROM V_EMPLOYEE t)
SELECT er.employee_id
  FROM employee_rows er
 WHERE er.rownum > 1

Using Inline view/Non-CTE Equivalent Alternative:

SELECT er.employee_id
  FROM (SELECT t.employee_id,
               ROW_NUMBER() OVER ( ORDER BY t.employee_id ) 'rownum'
          FROM V_EMPLOYEE t) er
 WHERE er.rownum > 1

Answer 2

SELECT  employee_id
FROM    (
        SELECT  employee_id, ROW_NUMBER() OVER (ORDER BY employee_id) AS rn
        FROM    V_EMPLOYEE
        ) q
WHERE   rn > 0
ORDER BY
        Employee_ID

Note that this filter is redundant: ROW_NUMBER() starts from 1 and is always greater than 0.

Answer 3

I think you want something like this:

SELECT employee_id 
FROM  (SELECT employee_id, row_number() 
       OVER (order by employee_id) AS 'rownumber' 
       FROM V_EMPLOYEE) TableExpressionsMustHaveAnAliasForDumbReasons
WHERE rownumber > 0

Answer 4

I feel like all the answers showing use of a CTE or Sub Query are sufficient fixes for this, but I don't see anyone getting to the heart of why OP has a problem. The reason why what OP suggested doesn't work is due to logical query processing order here:

1. FROM
2. ON
3. JOIN
4. WHERE
5. GROUP BY
6. WITH CUBE/ROLLUP
7. HAVING
8. SELECT
9. DISTINCT
10. ORDER BY
11. TOP
12. OFFSET/FETCH

I believe this contributes to the answer greatly, because it explains why issues like this one occur. WHERE is always processed before SELECT making a CTE or Sub Query necessary for many functions. You will see this a lot in SQL Server.