How to select top X from a Row_number in SQL Server ? - sql-server

Question

I have a data sample, and now i want to get data using TOP X combine ROW_NUMBER()
IndexNo ProductName
1 Black
2 Blue
3 Brown
4 Green
5 Red
6 White
7 Yellow
As follow in this case, i want to get the data, which after run SQL Statement, result as
IndexNo ProductName
3 Brown
4 Green
5 Red
I use this sql statement for this case, but i get this error Invalid column name 'IndexNo' , this is sql statement .
SELECT TOP 3 ROW_NUMBER() OVER(ORDER BY TEMPA.ProductName) AS IndexNo, TEMPA.ProductName
FROM (
SELECT DISTINCT ProductName FROM PRODUCTS WHERE ProductType ='Food'
) AS TEMPA
WHERE IndexNo between 3 and 5

Answer 1

You could use another level of subquery with parentheses.
SELECT TOP 3 * FROM
( SELECT ROW_NUMBER() OVER(ORDER BY TEMPA.ProductName) AS IndexNo, TEMPA.ProductName
FROM (
SELECT DISTINCT ProductName FROM PRODUCTS
) AS TEMPA
) as TEMPB
WHERE IndexNo between 3 and 5
DEMO

Answer 2

You need to wrap your ROW_NUMBER into Common Table Expression and apply between on the outer level:
with cte as (
SELECT ROW_NUMBER() OVER(ORDER BY TEMPA.ProductName) AS IndexNo, TEMPA.ProductName
FROM (
SELECT DISTINCT ProductName FROM PRODUCTS WHERE ProductType ='Food'
) AS TEMPA
) select top 3 * from cte
WHERE cte.IndexNo between 3 and 5

Answer 3

You need to create the ROW_NUMBER() in one scope and filter it in another scope...
SELECT
*
FROM
(
SELECT *, ROW_NUMBER() OVER (ORDER BY x) AS ix FROM example
)
indexed_example
WHERE
ix BETWEEN 3 AND 5
This is the NOT same for TOP and ORDER BY, as these are applied after the SELECT and WHERE clauses, so this would work fine...
SELECT TOP(3)
*,
ROW_NUMBER() OVER (ORDER BY id DESC) ix
FROM
example
ORDER BY
ix
This is especially useful to your case when using ORDER BY ? OFFSET ? FETCH ? instead of TOP.
SELECT
*,
ROW_NUMBER() OVER (ORDER BY id DESC) ix
FROM
example
ORDER BY
ix DESC
OFFSET 2 ROWS -- Skip 2 rows
FETCH NEXT 3 ROWS ONLY -- Fetch the 3rd, 4th and 5th rows.
In your example, you're also using DISTINCT which is applied after the SELECT values are calculated, but you could use GROUP BY instead as it is applied before the SELECT values are calculated.
SELECT
ROW_NUMBER() OVER (ORDER BY Products.ProductName) ix,
Products.ProductName
FROM
Products
WHERE
Products.ProductType = 'Food'
GROUP BY
Products.ProductName
ORDER BY
ix DESC
OFFSET 2 ROWS
FETCH NEXT 3 ROWS ONLY
All the joins in the FROM clause first (nothing to do in your case)
Apply the WHERE clause
Apply the GROUP BY clause (same effect as your DISTINCT)
Calculate the SELECT values, including the ROW_NUMBER()
Apply the ORDER BY including the OFFSET and FETCH NEXT clauses
Everything you wanted, without needing to next anything in sub-queries.