How can I combine multiple rows into a comma-delimited list in SQL Server? [duplicate]

Question

Possible Duplicate:
SQL Server: Can I Comma Delimit Multiple Rows Into One Column?

I have Table X(X_ID, X_Name) is 1-M with Table Y(Y_ID, Y_Value)

Table X:

X_ID    X_Name
----    ------
12      foo
14      foo2
16      foo3

Table Y:

X_ID    Y_Value
----    -------
12      A
12      B
14      C
14      D
14      E
16      F
16      G

How to get the following result using T-Sql ?

X_ID   X_Name   Y_Value
----   ------   ------
12     foo      A,B
14     foo2     C,D,E
16     foo3     F,G

Thanks

Answer 1

SELECT X.X_ID, X.X_Name, Y_Values = STUFF((SELECT N',' + Y_Value FROM dbo.Y
  WHERE Y.X_ID = X.X_ID
  FOR XML PATH(''), 
  TYPE).value(N'./text()[1]', N'nvarchar(max)'), 1, 1, N'')
  FROM dbo.X;

In SQL Server 2017 and Azure SQL Database, you can use the new STRING_AGG() function:

SELECT x.X_ID, x.X_Name, 
    Y_Values = STRING_AGG(Y.Y_Value,',')
  FROM dbo.X
  INNER JOIN dbo.Y
  ON X.X_ID = Y.X_ID
  GROUP BY x.X_ID, x.X_Name;

If you don't like the default order, you can specify it using WITHIN GROUP:

SELECT x.X_ID, x.X_Name, 
    Y_Values = STRING_AGG(Y.Y_Value,',') WITHIN GROUP (ORDER BY Y.Y_Value)
  FROM dbo.X
  INNER JOIN dbo.Y
  ON X.X_ID = Y.X_ID
  GROUP BY x.X_ID, x.X_Name;