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

Using the Stuff and for xml path operator to concatenate rows to string :Group By two columns -->

CREATE TABLE #YourTable ([ID] INT, [Name] CHAR(1), [Value] INT)

INSERT INTO #YourTable ([ID],[Name],[Value]) VALUES (1,'A',4)
INSERT INTO #YourTable ([ID],[Name],[Value]) VALUES (1,'B',8)
INSERT INTO #YourTable ([ID],[Name],[Value]) VALUES (1,'B',5)
INSERT INTO #YourTable ([ID],[Name],[Value]) VALUES (2,'C',9)

-- retrieve each unique id and name columns and concatonate the values into one column
SELECT 
  [ID], 
  STUFF((
    SELECT ', ' + [Name] + ':' + CAST([Value] AS VARCHAR(MAX)) -- CONCATONATES EACH APPLICATION : VALUE SET      
    FROM #YourTable 
    WHERE (ID = Results.ID and Name = results.[name] ) 
    FOR XML PATH(''),TYPE).value('(./text())[1]','VARCHAR(MAX)')
  ,1,2,'') AS NameValues
FROM #YourTable Results
GROUP BY ID


SELECT 
  [ID],[Name] , --these are acting as the group by clause
  STUFF((
    SELECT ', '+  CAST([Value] AS VARCHAR(MAX)) -- CONCATONATES THE VALUES FOR EACH ID NAME COMBINATION 
    FROM #YourTable 
    WHERE (ID = Results.ID and Name = results.[name] ) 
    FOR XML PATH(''),TYPE).value('(./text())[1]','VARCHAR(MAX)')
  ,1,2,'') AS  NameValues
FROM #YourTable Results
GROUP BY ID, name

DROP TABLE #YourTable