Insert a Comma Separator Between ResultSet of a SQL Table Column

Consider we have a table dbo.User, and we need to get all UserIDs separated by comma the apply below script:

Example:

Select Top 5 UserID From dbo.User

gives output as below

UserID
1
2
3
4
5

DECLARE @UserID VARCHAR(MAX)

SELECT @USERID = COALESCE(@USERID+',' , '') + UserID
FROM dbo.User
SELECT @USERID

This yields output as 1,2,3,4,5,....