How to use GROUP BY to concatenate strings in SQL Server?

Question

How do I get:

id       Name       Value
1          A          4
1          B          8
2          C          9

to

id               


        

Answer 1

This kind of question is asked here very often, and the solution is going to depend a lot on the underlying requirements:

https://stackoverflow.com/search?q=sql+pivot

and

https://stackoverflow.com/search?q=sql+concatenate

Typically, there is no SQL-only way to do this without either dynamic sql, a user-defined function, or a cursor.

Answer 2

using XML path will not perfectly concatenate as you might expect... it will replace "&" with "&" and will also mess with <" and "> ...maybe a few other things, not sure...but you can try this

I came across a workaround for this... you need to replace:

FOR XML PATH('')
)

with:

FOR XML PATH(''),TYPE
).value('(./text())[1]','VARCHAR(MAX)')

...or NVARCHAR(MAX) if thats what youre using.

why the hell doesn't SQL have a concatenate aggregate function? this is a PITA.

Answer 3

didn't see any cross apply answers, also no need for xml extraction. Here is a slightly different version of what Kevin Fairchild wrote. It's faster and easier to use in more complex queries:

   select T.ID
,MAX(X.cl) NameValues
 from #YourTable T
 CROSS APPLY 
 (select STUFF((
    SELECT ', ' + [Name] + ':' + CAST([Value] AS VARCHAR(MAX))
    FROM #YourTable 
    WHERE (ID = T.ID) 
    FOR XML PATH(''))
  ,1,2,'')  [cl]) X
  GROUP BY T.ID

Answer 4

Another example without the garbage: ",TYPE).value('(./text())[1]','VARCHAR(MAX)')"

WITH t AS (
    SELECT 1 n, 1 g, 1 v
    UNION ALL 
    SELECT 2 n, 1 g, 2 v
    UNION ALL 
    SELECT 3 n, 2 g, 3 v
)
SELECT g
        , STUFF (
                (
                    SELECT ', ' + CAST(v AS VARCHAR(MAX))
                    FROM t sub_t
                    WHERE sub_t.g = main_t.g
                    FOR XML PATH('')
                )
                , 1, 2, ''
        ) cg
FROM t main_t
GROUP BY g

Input-output is

*************************   ->  *********************
*   n   *   g   *   v   *       *   g   *   cg      *
*   -   *   -   *   -   *       *   -   *   -       *
*   1   *   1   *   1   *       *   1   *   1, 2    *
*   2   *   1   *   2   *       *   2   *   3       *
*   3   *   2   *   3   *       *********************
*************************   

Answer 5

Just to add to what Cade said, this is usually a front-end display thing and should therefore be handled there. I know that sometimes it's easier to write something 100% in SQL for things like file export or other "SQL only" solutions, but most of the times this concatenation should be handled in your display layer.

Answer 6

Let's get very simple:

SELECT stuff(
    (
    select ', ' + x from (SELECT 'xxx' x union select 'yyyy') tb 
    FOR XML PATH('')
    )
, 1, 2, '')

Replace this line:

select ', ' + x from (SELECT 'xxx' x union select 'yyyy') tb

With your query.