How to concatenate many rows with same id in sql?

Question

My table contains the details like with two fields:

ID      DisplayName
1        Editor
1        Reviewer
7        EIC
7        Editor
7        Reviewer
7        Editor
19       EIC
19       Editor
19       Reviewer

I want get the unique details with DisplayName like

1 Editor,Reviewer 7 EIC,Editor,Reviewer

Don't get duplicate value with ID 7

How to combine DisplayName Details? How to write the Query?

Answer 1

In SQL-Server you can do it in the following:

QUERY

SELECT id, displayname = 
    STUFF((SELECT DISTINCT ', ' + displayname
           FROM #t b 
           WHERE b.id = a.id 
          FOR XML PATH('')), 1, 2, '')
FROM #t a
GROUP BY id

TEST DATA

create table #t 
(
id int,
displayname nvarchar(max)
)

insert into #t values    
 (1 ,'Editor')
,(1 ,'Reviewer')
,(7 ,'EIC')
,(7 ,'Editor')
,(7 ,'Reviewer')
,(7 ,'Editor')
,(19,'EIC')
,(19,'Editor')
,(19,'Reviewer')

OUTPUT

id  displayname
1   Editor, Reviewer
7   Editor, EIC, Reviewer
19  Editor, EIC, Reviewer