Using COALESCE function to make values separated with commas

Question

I have a table (EMP) I know that using the COALESCE function we can get the values of any column in this way

23,23,45,34

SELECT          


        

Answer 1

Isnull Function will also give us the same result

DECLARE @List VARCHAR(8000)

SELECT @List = ISNULL(@List + ',', '') + CAST(OfferID AS VARCHAR)
FROM   Emp
WHERE  EmpID = 23

SELECT @List 

Answer 2

DECLARE @List VARCHAR(8000)

SELECT @List = COALESCE(@List + ',', '') + CAST(OfferID AS VARCHAR)
FROM   Emp
WHERE  EmpID = 23

SELECT @List 

This approach to aggregate concatenation is not guaranteed to work. If you are on at least SQL Server 2005 XML PATH or CLR aggregates are preferred.

The definitive article on the subject is Concatenating Row Values in Transact-SQL

Answer 3

Description

I have done this using COALESCE in the past too, but i suggest another approach because you dont need a variable. Use the T-SQL function STUFF to get this done.

Sample

SELECT STUFF((
    select ','+ cast(OfferID as nvarchar(255)) 
    from Emp b
    WHERE a.EmpID= b.EmpID
    FOR XML PATH('')
    ),1,1,'') AS COLUMN2
FROM Emp a
GROUP BY a.EmpID

More Information

STUFF (Transact-SQL)

Answer 4

Description

dknaack solution has some drawbacks when text contains some XML caracters like <, which are html-entitized as <. This can be solved using the TYPE directive which sends the response as xml, then extract the raw value as string.

There are plenty more solutions to the problem in this article : Concatenating Row Values in T-SQL

Sample

SELECT STUFF((
    select ','+ cast(OfferID as nvarchar(255)) 
    from Emp b
    WHERE a.EmpID= b.EmpID
    FOR XML PATH(''), TYPE
    ).value('.', 'varchar(max)')
    ,1,1,'') AS COLUMN2
FROM Emp a
GROUP BY a.EmpID