How to get comma-separated values in multiple rows in SQL

Question

To return data as comma separated values, I want to develop a table valued function in SQL Server.

For example table: tbl

ID | Value
---+-------
 1 | 100
 1 | 200
 1 | 300     
 1 | 400 

Now when I execute the query using the function Func1(value)

SELECT Func1(Value) 
FROM tbl 
WHERE ID = 1

Output that I want is: 100,200,300,400

Can someone please help me with this?

Answer 1

Test Data

DECLARE @Table1 TABLE(ID INT, Value INT)
INSERT INTO @Table1 VALUES (1,100),(1,200),(1,300),(1,400)

Query

SELECT  ID
       ,STUFF((SELECT ', ' + CAST(Value AS VARCHAR(10)) [text()]
         FROM @Table1 
         WHERE ID = t.ID
         FOR XML PATH(''), TYPE)
        .value('.','NVARCHAR(MAX)'),1,2,' ') List_Output
FROM @Table1 t
GROUP BY ID

Result Set

╔════╦═════════════════════╗
║ ID ║     List_Output     ║
╠════╬═════════════════════╣
║  1 ║  100, 200, 300, 400 ║
_