Question

I made the following function in SQL Server 2008 earlier this week that takes two parameters and uses them to select a column of “detail” records and returns them as a single varchar list of comma separated values. Now that I get to thinking about it, I would like to take this table and application-specific function and make it more generic.

I am not well-versed in defining SQL functions, as this is my first. How can I change this function to accept a single “column” worth of data, so that I can use it in a more generic way?

Instead of calling:

SELECT ejc_concatFormDetails(formuid, categoryName)

I would like to make it work like:

SELECT concatColumnValues(SELECT someColumn FROM SomeTable)

Here is my function definition:

FUNCTION [DNet].[ejc_concatFormDetails](@formuid AS int, @category as VARCHAR(75))
RETURNS VARCHAR(1000) AS
BEGIN
 DECLARE @returnData VARCHAR(1000)
 DECLARE @currentData VARCHAR(75)
 DECLARE dataCursor CURSOR FAST_FORWARD FOR
  SELECT data FROM DNet.ejc_FormDetails WHERE formuid = @formuid AND category = @category

 SET @returnData = ''

 OPEN dataCursor

 FETCH NEXT FROM dataCursor INTO @currentData
 WHILE (@@FETCH_STATUS = 0)
 BEGIN
  SET @returnData = @returnData + ', ' + @currentData
  FETCH NEXT FROM dataCursor INTO @currentData
 END

 CLOSE dataCursor
 DEALLOCATE dataCursor

 RETURN SUBSTRING(@returnData,3,1000)
END

As you can see, I am selecting the column data within my function and then looping over the results with a cursor to build my comma separated varchar.

How can I alter this to accept a single parameter that is a result set and then access that result set with a cursor?

Answer 1

You can use table-valued parameters:

CREATE FUNCTION MyFunction(
    @Data AS TABLE (
        Column1 int,
        Column2 nvarchar(50),
        Column3 datetime
    )
)
RETURNS NVARCHAR(MAX)
AS BEGIN
    /* here you can do what you want */
END