A Little FOR XML PATH Nugget

A very small post this one, covering a little nugget that I’d almost forgot until it came up trumps again this week; TSQL FOR XML PATH can be a nice solution for concatenation of strings across rows (in a given column).

It’s fairly common to have the need to concatenate column based data, as the following example illustrates:

--Standard concatenation of column values (comma separated, produces multiple rows)
SELECT 
FORENAME 
+ ', ' 
+ SURNAME AS [FULL_NAME]
FROM dbo.tblTEST t
WHERE t.ID < 4;

However, don’t forget that working through and concatenating row based data, in a particular column, can be achieved simply using the FOR XML PATH construct, just like this:

--Concatenation of row values for a particular column (imagine we wanted comma separated forenames for example) - Provides a single column as structured
SELECT
CONVERT                                     --Conversion required to an NVARCHAR(VALUE) (MAX depending on string size) - The result will be XML when using FOR XML PATH initially
(
    NVARCHAR(100)
    ,
    (
        SELECT
        t.FORENAME + 
        CASE
            WHEN t.ID < 3                    --Don't add a comma after the last value (just for illustration purposes)
            THEN ', '
            ELSE ''
        END
        FROM dbo.tblTEST t
        WHERE t.ID < 4
        FOR XML PATH('')					 --Specify FOR XML PATH using an empty string (we don't want a wrapping element when concatenating strings)
    )
) AS [COMMA_SEPARATED_FORENAMES];

Interesting use of FOR XML PATH that’s well worth keeping in mind, it can come in dead handy. Apologies for the Short and sweet post; it’s the order of the day! I’ve managed to pick up the dreaded lurgy so I’m dosed up on medication and drinking a tonne of coffee! Here’s hoping that this post makes sense when I read it later on.

Until the next time, bye for now!