Using MS SQL Server 2005, how can I consolidate detail records into a single comma separated list

Question

BACKGROUND:I am running MS2005. I have a MASTER table (ID, MDESC) and a DETAIL table (MID, DID, DDESC) with data as follows

1 MASTER_1
2 MASTER_2
1 L1 DETAIL_M1_L1
1 L2 DETAIL_M1_L2
1 L3 DETAIL_M1_L3
2 L1 DETAIL_M2_L1
2 L2 DETAIL_M2_L2

If I join the tables with

SELECT M.*, D.DID FROM MASTER M INNER JOIN DETAIL D on M.ID = D.MID

I get a list like the following:

1 MASTER_1 L1
1 MASTER_1 L2
1 MASTER_1 L3
2 MASTER_2 L1
2 MASTER_2 L2

QUESTION: Is there any way to use a MS SQL select statement to get the detail records into a comma separated list like this:

1 MASTER_1 "L1, L2, L3"
2 MASTER_2 "L1, L2"

Answer 1

coalesce is your friend.

declare @CSL vachar(max)

set @CSL = NULL
select @CSL = coalesce(@CSL + ', ', '') + cast(DID as varchar(8))
from MASTER M INNER JOIN DETAIL D on M.ID = D.MID

select @CSL

This will not work well for a generalized query (i.e. works great for a single master record).

You could drop this into a function... but that may not give you the performance you need/want.

Answer 2

This is the purpose of MySQL's GROUP_CONCAT() aggregate function. Unfortunately, it's not very easy to duplicate this function in other RDBMS brands that don't support it.

See http://stackoverflow.com/questions/451415/simulating-groupconcat-mysql-function-in-ms-sql-server-2005

Answer 3

I think you need a Fucntion for this to work properly in recent version of SQL Server:

http://sqljunkies.com/WebLog/amachanic/archive/2004/11/10/5065.aspx?Pending=true

Answer 4

You need a function:-

 CREATE FUNCTION [dbo].[FN_DETAIL_LIST]
 (
     @masterid int
 )
 RETURNS varchar(8000)
 AS 
 BEGIN
     DECLARE @dids varchar(8000)

     SELECT @dids = COALESCE(@dids + ', ', '') + DID
     FROM DETAIL
     WHERE MID = @masterid
     RETURN @dids
 END

Usage:-

SELECT MASTERID, [dbo].[FN_DETAIL_LIST](MASTERID) [DIDS]
FROM MASTER

Answer 5

Thanks to the concept in the link from Bill Karwin, it's the CROSS APPLY that makes it work

SELECT ID, DES, LEFT(DIDS, LEN(DIDS)-1) AS DIDS
 FROM MASTER M1 INNER JOIN DETAIL D on M1.ID = D.MID 
  CROSS APPLY (
    SELECT DID + ', '
    FROM MASTER M2 INNER JOIN DETAIL D on M2.ID = D.MID 
    WHERE M1.ID = M2.ID
    FOR XML PATH('')
   ) pre_trimmed (DIDS)
GROUP BY ID, DES, DIDS

RESULTS:

ID  DES        DIDS
--- ---------- ---------------
1   MASTER_1   L1, L2, L3
2   MASTER_2   L1, L2