PIVOT without aggregate function ID as column names - sql

Question

I have a query
SELECT a.Name, b.Date FROM
Table1 a
JOIN Table2 b on a.deviceID=b.id
where a.date > '2022-10-01'
Which gives me result
Name Date
A1 '2022-10-01 12:13'
A2 '2022-10-02 14:15'
A2 '2022-10-02 15:16'
A5 '2022-10-03 16:19'
etc.
The result I want to achieve is
A1 A2 A5
'2022-10-01 12:13' '2022-10-02 14:15''2022-10-03 16:19'
'2022-10-02 15:16'
The perfect result would be to receive only one date of each day. Can I do it with pivot?

Answer 1

Pivoting cannot be done (in T-SQL) without aggregation. As for what you want to achieve, seems you need to PIVOT/conditionally aggregate on the value of Name and group on the value of a ROW_NUMBER.
I, personally, prefer using conditional aggregation over the restrictive PIVOT operator, but I have included examples of both:
USE Sandbox;
GO
CREATE TABLE #YourData (Name char(2),
Date datetime2(0));
GO
INSERT INTO #YourData (Name,
Date)
VALUES('A1','2022-10-01T12:13:00'),
('A2','2022-10-02T14:15:00'),
('A2','2022-10-02T15:16:00'),
('A5','2022-10-03T16:19:00');
GO
WITH RNs AS(
SELECT [Name],
[Date],
ROW_NUMBER() OVER (PARTITION BY [Name] ORDER BY [Date]) AS RN
FROM #YourData)
SELECT MAX(CASE [Name] WHEN 'A1' THEN [Date] END) AS A1,
MAX(CASE [Name] WHEN 'A2' THEN [Date] END) AS A2,
MAX(CASE [Name] WHEN 'A5' THEN [Date] END) AS A5
FROM RNs
GROUP BY RN;
GO
SELECT P.A1,
P.A2,
P.A5
FROM (SELECT [Name],
[Date],
ROW_NUMBER() OVER (PARTITION BY [Name] ORDER BY [Date]) AS RN
FROM #YourData)YD
PIVOT(MAX([date])
FOR [Name] IN (A1,A2,A5))P;
GO
DROP TABLE #YourData;

Answer 2

If you want to pivot but keep all your related values in the same field rather than creating fake rows, you can use STRING_AGG. You can replace the "," separator with a CHAR(10), or perhaps an HTML to add a line break. You won't see it in SSMS but depending on your front end, that would render the two items, one under each other.
DROP TABLE IF EXISTS #YourData
CREATE TABLE #YourData (Name char(2),
Date datetime2(0));
GO
INSERT INTO #YourData (Name,
Date)
VALUES('A1','2022-10-01T12:13:00'),
('A2','2022-10-02T14:15:00'),
('A2','2022-10-02T15:16:00'),
('A5','2022-10-03T16:19:00');
GO
DECLARE #Seperator VARCHAR(10) = ' , '
SELECT
[A1] , [A2], [A3], [A4], [A5]
FROM
(
SELECT name, STRING_AGG(date,#Seperator) AS Dates
FROM #YourData
GROUP BY Name
) AS SourceTable
PIVOT
(
MAX(Dates)
FOR Name IN ([A1], [A2], [A3], [A4], [A5])
) AS PivotTable;