SQL

sql column values comma separated

SELECT STRING_AGG(columnName,',') from tableName

sql server: select column values as comma separated string

 DECLARE @SQL AS VARCHAR(8000)
SELECT @SQL = ISNULL(@SQL+',','') + ColumnName FROM TableName
SELECT @SQL

get comma separated values in sql server

STRING_AGG: Applies to SQL Server 2017 (14.x) and later 

DECLARE @Table2 TABLE(ID INT, Value INT);
INSERT INTO @Table1 VALUES (1,100),(1,200),(1,300),(1,400);

SELECT ID , STRING_AGG([Value], ', ') AS List_Output
FROM @Table2
GROUP BY ID;

-- OR 

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

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