SQL query GROUP BY groups - sql

Question

I have something like this:
id
name
totalAmount
1
name1
10
2
name1
20
3
name1
25
4
name2
5
5
name2
12
And need to looks like this:
id's
name
totalAmount
1,2
name1
30
2,3
name1
45
1,3
name1
35
1,2,3
name1
55
4,5
name2
17
I'm using the STRING_AGG but don't know how to separated in the first 3 id's.

Answer 1

Here is a recursive version which can handle more than 3 ids for a name and returns all possible combinations. As Dai points out though, take care as the number of combinations quickly mushrooms. But if your real data is like your example (normally 2-3 ids per name) than it should be fine.
Worth noting that I did this for fun. Probably you would be best just storing the raw data and doing this kind of shenanigans in the application layer.
CREATE TABLE #data
(
id INT,
[name] VARCHAR(10),
totalAmount INT
);
INSERT INTO #data
VALUES
(1, 'name1', 10),
(2, 'name1', 20),
(3, 'name1', 25),
(4, 'name2', 5),
(5, 'name2', 12);
WITH cte (name, ids, maxid, tot) AS
(
SELECT a.name,
CONVERT(VARCHAR(8000), CONVERT(VARCHAR(10), a.id) + ',' + CONVERT(VARCHAR(10), b.id) ) AS ids,
b.id AS maxid,
a.totalAmount + b.totalAmount AS tot
FROM #data a
INNER JOIN #data b ON b.name = a.name AND a.id < b.id
UNION ALL
SELECT cte.name,
CONVERT(VARCHAR(8000), cte.ids + ',' +CONVERT(VARCHAR(10), a.id)),
a.id AS maxid,
cte.tot + a.totalAmount
FROM cte
INNER JOIN #data a ON cte.name = a.name
WHERE a.id > cte.maxid
)
SELECT ids, name, tot
FROM cte

Answer 2

-- *** Test Data ***
CREATE TABLE #t
(
id int NOT NULL PRIMARY KEY
,[name] nvarchar(30) NOT NULL
,totalAmount money NOT NULL
);
INSERT INTO #t
VALUES (1, 'name1', 10)
,(2, 'name1', 20)
,(3, 'name1', 25)
,(4, 'name2', 5)
,(5, 'name2', 12);
-- *** End Test Data ***
SELECT CAST(T1.id AS varchar(10))
+ ',' + CAST(T2.id AS varchar(10)) AS ids
,T1.[name] AS [name]
,T1.totalAmount + T2.totalAmount AS totalAmount
FROM #t T1
JOIN #t T2
ON T1.[name] = T2.[name]
WHERE T1.id < T2.id
UNION ALL
SELECT CAST(T1.id AS varchar(10))
+ ',' + CAST(T2.id AS varchar(10))
+ ',' + CAST(T3.id AS varchar(10)) AS ids
,T1.[name] AS [name]
,T1.totalAmount + T2.totalAmount + T3.totalAmount AS totalAmount
FROM #t T1
JOIN #t T2
ON T1.[name] = T2.[name]
JOIN #t T3
ON T1.[name] = T3.[name]
WHERE T1.id < T2.id
AND T2.id < T3.id;