How to select only first ROW_NUMBER combined with SUM - sql-server

Question

I like to group my table by [ID] while using SUM and also bring back
[Product_Name] of the top ROW_NUMBER - not sure if I should use ROW_NUMBER, GROUPING SETS or loop through everything with FETCH... this is what I tried:
DECLARE #SampleTable TABLE
(
[ID] INT,
[Price] MONEY,
[Product_Name] VARCHAR(50)
)
INSERT INTO #SampleTable
VALUES (1, 100, 'Product_1'), (1, 200, 'Product_2'),
(1, 300, 'Product_3'), (2, 500, 'Product_4'),
(2, 200, 'Product_5'), (2, 300, 'Product_6');
SELECT
[ID],
[Product_Name],
[Price],
SUM([Price]) OVER (PARTITION BY [ID]) AS [Price_Total],
ROW_NUMBER() OVER (PARTITION BY [ID] ORDER BY [ID]) AS [Row_Number]
FROM
#SampleTable T1
My desired results - only two records:
1 Product_1 100.00 600.00 1
2 Product_4 500.00 1000.00 1
Any help or guidance is highly appreciated.
UPDATE:
I end up using what Prateek Sharma suggested in his comment, to simply wrap the query with another SELECT WHERE [Row_Number] = 1
SELECT * FROM
(
SELECT
[ID]
,[Product_Name]
,[Price]
,SUM([Price]) OVER (PARTITION BY [ID]) AS [Price_Total]
,ROW_NUMBER() OVER (PARTITION BY [ID] ORDER BY [ID]) AS [Row_Number]
FROM #SampleTable
) MultipleRows
WHERE [Row_Number] = 1

Answer 1

You should have a column on which you will perform ORDER BY for ROW_NUMBER(). In this case if you want to only rely on the table self index then it's OK to use ID column for ORDER BY.
Hence your query is correct and you can go with it.
Other option is to use WITH TIES clause. BUT again, If you will use WITH TIES clause with the ORDER BY on ID column then performance will be very poor. WITH TIES only performs well if you have well defined index. And, then can use that indexed column with WITH TIES clause.
SELECT TOP 1 WITH TIES *
FROM (
SELECT [ID]
,[Product_Name]
,[Price]
,SUM([Price]) OVER (PARTITION BY [ID]) AS [Price_Total]
FROM #SampleTable
) TAB
ORDER BY ROW_NUMBER() OVER (PARTITION BY [ID] ORDER BY <IndexedColumn> DESC)
This query may help you bit. But remember, it is also not going to provide better performance than the query written by you. It is only reducing the line of code.

Answer 2

One option is using the WITH TIES clause. No extra field RN.
Hopefully, you have a proper sequence number or date which can be used in either the sum() over or in the final row_number() over
Example
SELECT Top 1 with ties *
From (
Select [ID]
,[Product_Name]
,[Price]
,SUM([Price]) OVER (PARTITION BY [ID]) AS [Price_Total]
FROM #SampleTable T1
) A
Order By ROW_NUMBER() OVER (PARTITION BY [ID] ORDER BY [Price_Total] Desc)
Returns
ID Product_Name Price Price_Total
1 Product_1 100.00 600.00
2 Product_4 500.00 1000.00

Answer 3

There is no "top ROW_NUMBER" unless you have a column that defines ordering.
If you just want an arbitary row per id you can use the below. To deterministically pick one you would need to order by deterministic unique criteria.
DECLARE #SampleTable TABLE
(
ID INT,
Price MONEY,
Product_Name VARCHAR(50),
INDEX cix CLUSTERED (ID)
);
INSERT INTO #SampleTable
VALUES (1,100,'Product_1'),
(1,200,'Product_2'),
(1,300,'Product_3'),
(2,500,'Product_4'),
(2,200,'Product_5'),
(2,300,'Product_6');
WITH T AS
(
SELECT *,
OrderingColumn = ROW_NUMBER() OVER (ORDER BY (SELECT 0))
FROM #SampleTable
)
SELECT ID,
SUBSTRING(MIN(CONCAT(STR(OrderingColumn), Product_Name)), 11, 50) AS Product_Name,
CAST(SUBSTRING(MIN(CONCAT(STR(OrderingColumn), Price)), 11, 50) AS MONEY) AS Price,
SUM(Price) AS Price_Total
FROM T
GROUP BY ID
The plan for this is pretty efficient as it is able to use the index ordered by id and has no additional sorts, spools, or passes through the table.