Cannot add STRING_AGG(column, ',') into overall Query - sql

Question

I'm running SQL Server 2017 and my query works perfectly fine, with the exception of when I try to add the following:
,STRING_AGG (TemplateID, ',') as Result1
This is a Stored Procedure supporting an SSRS report in the end.
I need the templateID's to be in a result which would be a comma separated list of values like "1,3,5,12,14,33,44,100,107" (just as an example) Also like to only select Distinct ones if possible.
When I add the above to my overall Stored Procedure, I get the following error in Management Studio:
Msg 8120, Level 16, State 1, Procedure sp_ChangesByUserDetail, Line 11 [Batch Start Line 7]
Column 'ChangeDetail.DisplayName' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
Here is my entire SELECT statement.
SELECT DisplayName, IsDeleted, TemplateID,TemplateName, Version, Name, UpdatedBy, DataTable, ID, IsVirtual,
DATEADD(minute, DATEDIFF(minute, getutcdate(), GETDATE()), AddedDate) As AddedDate,
CONVERT(varchar(8), DATEADD(minute, DATEDIFF(minute, getutcdate(), GETDATE()), AddedDate), 108)
AS AddedTime, AttachmentContent, UserName, UpdatedDate,
cast(datediff(second, '1970-01-01 00:00:00', AddedDate) as varchar ) + '000' as millisec
,STRING_AGG (TemplateID, ',') as Result1
FROM ChangeDetail WITH (NOLOCK)
where UpdatedBy in (select s from fn_SplitLarge(',',#In_ModifiedBy))
and templatename in (select s from fn_SplitLarge(',',#In_ItemType))
and DATEADD(minute, DATEDIFF(minute, getutcdate(), GETDATE()), AddedDate) between #In_StartDate + #In_StartTime and #In_EndDate + #In_EndTime
Thoughts?

Answer 1

Reason is not having the fields grouped by. Also note that the field for which you group by shouldn't be in the list of fields (and the Name)
ex.
Create table #t (Id int, TemplateName varchar(100))
insert into #t values
(1,'aaa'), (1,'bbb'),(1,'ccc'),(2,'ppp'),(2,'qqq'),(3,'XXX'),(3,'YYY'),(4,'ZZZ ')
SELECT ID, TemplateName FROM #T
-- FOLLOWING DOESN'T WORK
-- SELECT ID, TemplateName, STRING_AGG (TemplateName, ',') as Result1 FROM #T
-- FOLLOWING WORKS
SELECT ID, STRING_AGG (TemplateName, ',') as Result1 FROM #T
GROUP BY ID
So you can make your query as follows:
Select DisplayName, IsDeleted, Version, Name, UpdatedBy, DataTable, ID, IsVirtual,
AddedDate,AddedTime, AttachmentContent, UserName, UpdatedDate, millisec
,STRING_AGG (TemplateID, ',') as Result1
from
(
SELECT DisplayName, IsDeleted, TemplateID,TemplateName, Version, Name, UpdatedBy, DataTable, ID, IsVirtual,
DATEADD(minute, DATEDIFF(minute, getutcdate(), GETDATE()), AddedDate) As AddedDate,
CONVERT(varchar(8), DATEADD(minute, DATEDIFF(minute, getutcdate(), GETDATE()), AddedDate), 108) AS AddedTime,
AttachmentContent, UserName, UpdatedDate,
cast(datediff(second, '1970-01-01 00:00:00', AddedDate) as varchar ) + '000' as millisec
FROM ChangeDetail WITH (NOLOCK)
where UpdatedBy in (select s from fn_SplitLarge(',',#In_ModifiedBy))
and templatename in (select s from fn_SplitLarge(',',#In_ItemType))
and DATEADD(minute, DATEDIFF(minute, getutcdate(), GETDATE()), AddedDate)
between #In_StartDate + #In_StartTime and #In_EndDate + #In_EndTime
) Q
Group By DisplayName, IsDeleted, Version, Name, UpdatedBy, DataTable, ID, IsVirtual,
AddedDate,AddedTime, AttachmentContent, UserName, UpdatedDate, millisec