Sql Server Flatten Rows to Columns - sql

Question

I have a table that looks similar to this
RowNumber Value colIdx
1 A 1
1 Shimano Dura-Ace 2
2 B 1
2 SRAM eTap 2
3 C 1
3 Campagnolo Super Record 2
I want to flatten rows, and so far I have come up with the following
SELECT Rownumber,
stuff(
(SELECT DISTINCT ': ' + cast(value AS varchar(MAX))
FROM groupsets t2
WHERE t2.Rownumber = t1.Rownumber
FOR XML PATH('')),1,1,'')
FROM groupsets t1
GROUP BY Rownumber
ORDER BY Rownumber
However, the following is produced - I want for the single character to always prefix the value.
RowNumber Value
1 A: Shimano Dura-Ace
2 B: SRAM eTap
3 Campagnolo Super Record: D
I have created a SQL Fiddle here. I'm not sure how to order by colIdx without needing to expose it?
The expected output is:
RowNumber Value
1 A: Shimano Dura-Ace
2 B: SRAM eTap
3 D: Campagnolo Super Record

Answer 1

Datasets in SQL Server are never guaranteed to be returned in any specific order without using an ORDER BY clause.
If you need to guarantee that the single character will be returned first, you'll need to use an ORDER BY. For example:
SELECT Rownumber,
STUFF(CONVERT(varchar(MAX),(SELECT DISTINCT ': ' + [value] --Is the DISTINCT required here?
--Also, the CAST is not required, that goes on the outside of the SELECt, as you can see
FROM groupsets t2
WHERE t2.Rownumber = t1.Rownumber
ORDER BY LEN([value]) ASC
FOR XML PATH(''))),1,1,'')
FROM groupsets t1
GROUP BY Rownumber
ORDER BY Rownumber;

Answer 2

While digging a bit I saw some new feature in SQL Server 2017 (and azure). Here's a query that will work using a CTE + STRING_AGG (New feature).
WITH groupsetsOrdered AS
(
SELECT top 100000 rownumber, [value], [colIdx]
FROM groupsets
ORDER BY rownumber, colidx
)
select rownumber as [RowNumber], string_agg([value], ': ') as [Value]
from groupsetsOrdered
group by rownumber
order by rownumber
Dataset like:
CREATE TABLE groupsets
([Rownumber] varchar(1), [Value] varchar(max), [colidx] int)
;
INSERT INTO groupsets
([Rownumber], [Value], [colidx])
VALUES
('1', 'A',1),
('1', 'Shimano Dura-Ace',2),
('2', 'SRAM eTap',2),
('2', 'B',1),
('3', 'D',1),
('3', 'Campagnolo Super Record',2)
;
Result:
rownumber Value
1 A: Shimano Dura-Ace
2 B: SRAM eTap
3 D: Campagnolo Super Record
(Fiddle: http://sqlfiddle.com/#!18/707ec/9/0)