How to “Implode” (de-normalize/concat) multiple columns into a single column?

Question

I have a query which outputs something like this:

+-------+----+--------------+
| F_KEY | EV | OTHER_COLUMN |
+-------+----+--------------+
| 100   | 1  | ..         


        

Answer 1

You can do it easily enough with a function: Assumes you are going to be searching the same column/table all the time. Dynamic SQL needed if you want to be able to vary the columns/tables

CREATE FUNCTION [dbo].[fn_recursion]
(@F_KEY int)  
RETURNS varchar(2000) AS 
BEGIN 

    DECLARE @ReturnVal Varchar(2000)

    SELECT @ReturnVal = COALESCE(@ReturnVal + ', ', '') + EV
    FROM TABLE2 
    WHERE @F_KEY = @F_KEY

    RETURN ISNULL(@ReturnVal,'')

END
GO


SELECT
    F_KEY,
    EV = [dbo].[fn_recursion](F_KEY),
    OTHER_COLUMN
FROM
    TABLE1
JOIN
    TABLE2 ON F_KEY = TABLE2.ID
WHERE
    EVENT_TIME BETWEEN '2011-01-01 00:00:00.000' AND '2011-12-31 23:59:59.999'
ORDER BY
    EVENT_TIME ASC

GO

DROP FUNCTION [dbo].[fn_recursion]
GO