MSSQL - Concat the result of a query using IN

Question

In a MSSQL table ("username"), I have the two following records:

name   ¦  nickname
John      Johny
Marc      Marco

I'd like to do a query that would return "Johny, Marco" when I as k for the nicknames of John and Marc.

I've tried the following:

declare @consolidatedNicknames varchar(2000)
set @consolidatedNicknames = ''
select @consolidatedNicknames = @consolidatedNicknames + nickname + ';'
From username WHERE name IN ('John','Marc')

but it only returns me the nickname of 'John'.

How could it concat the nickname of 'John' AND 'Marc' ?

Many thanks.

Answer 1

Your sample code worked as expected for me. I've had a few problems with that method with large strings (50k characters or more). Here is a different version that I've found a bit more robust.

DECLARE @consolidatedNicknames varchar(2000)
SET @consolidatedNicknames = ''

SELECT @consolidatedNicknames = 
        STUFF((SELECT ', ' + username.nickname
                FROM username
                WHERE name IN ('John','Marc')
                FOR XML PATH(''),TYPE).value('.','VARCHAR(MAX)')
            , 1, 2, '')

Answer 2

STUFF and XML are what you need. Have a look at this article

Here is a function I have build to do something very similar.

CREATE FUNCTION [dbo].[CapOwnerList]
    (
    @Seperator nvarchar(100) = ','
    )

    RETURNS @ConcatValues TABLE
        (
        ID DECIMAL(28,0) NOT NULL
        ,VALUE NVARCHAR(MAX)
        )
    AS
    BEGIN
        DECLARE @TempTable TABLE (ID INT, VAL VARCHAR(MAX));

        INSERT INTO @TempTable (ID,VAL)
        SELECT  C2O.CAP_ID
                ,FP.NAME
        FROM    REL_CAP_HAS_BUS_OWNER C2O
        INNER JOIN
                FACT_PERSON FP
        ON      C2O.PERSON_ID = FP.ID
        ORDER BY
                FP.NAME
        ;

        IF RIGHT(@Seperator,1)<>' '
            SET @Seperator = @Seperator+' ';

        INSERT @ConcatValues
        SELECT  DISTINCT 
                T1.ID
                ,STUFF((SELECT @Seperator + T2.VAL FROM @TempTable AS T2 WHERE T2.ID = T1.ID FOR XML PATH('')), 1, LEN(@Seperator), '') AS VALS
        FROM    @TempTable AS T1;

        RETURN;
    END

GO