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T-SQL User defined function to concatenate column to CSV string

I had a  complicate (and buggy) T-SQLstored procedure, that concatenate fields from details table and show them as one field in the resultset of the main table(Itinerary and summary of itinerary items. I’ve looked in pivot functionality, but didn’t fint how to make it working in the way I needed. Furthermore, Pivot is available for SQL Server DB with compatibility level 90(aka SQL server 2005), but our db still has compatibility level 80(aka SQL server 2000). 

So I desided to write UDF to concatenate column values into CSV string for each row. Thanks to the discussion I’ve created UDF similar to the following:

Alter FUNCTION Components_ProvidersCsvForItinerary
      -- Add the parameters for the function here
      @ItineraryId int
RETURNS nvarchar(3000)
      -- Declare the return variable here
declare @keywords nvarchar(3000)
--Build your csv string of keywords
Select @keywords = null
SELECT @Keywords = Coalesce(@Keywords + ', ', '') +
from ProviderComponents IC
where IC.ItineraryID =@ItineraryID
      -- Return the result of the function
      RETURN @keywords
select dbo.Components_ProvidersCsvForItinerary (234563)
select top 10 ItineraryID, Replace(dbo.Components_ProvidersCsvForItinerary (ItineraryID),',','/')
 from ItineraryTable
order by ItineraryID Desc

Unfortunately, you can’t make it generic(tables and columns are different for each task), but it can be implemented as template.

May be Table variables and temporary tables(see original  discussion) have better performance, that UDF( Ididn’t test), but the UDF makes the code better structured and easier to read/understand.

By the way, I have similar function in ADO.Net – see TableColumnToString(DataTable tbl, string sColumnName, string delimeter) in My DataHelper class

This article is part of the GWB Archives. Original Author: Michael Freidgeim’s Blog

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