Can someone explain the STUFF and FOR XML PATH techniques in SQL Server?

Data and Databases
1

Hey SQL gurus! I’m scratching my head over this query:

SELECT ID, 
    abc = STUFF(
                 (SELECT ',' + name FROM temp1 FOR XML PATH ('')), 1, 1, ''
               ) 
FROM temp1 GROUP BY id

It works fine but I’m lost on how it actually does the job. Here’s what I’m trying to do:

I’ve got a table with an Id column and a Name column. Multiple rows have the same Id but different Names. I want to squish all the Names for each Id into one comma-separated string.

For example:

Id | Name
1 | apple
1 | banana
1 | cherry

Should become:

Id | Names
1 | apple,banana,cherry

Can anyone break down how STUFF and FOR XML PATH are making this happen? Or is there an easier way to do this? Thanks in advance!

2

hey sophia39! that query looks tricky, huh? have u tried using string_agg() instead? it’s a bit simpler for concatenating strings. but if ur stuck with older SQL versions, the STUFF+XML method is pretty clever. what version of SQL Server r u using? maybe we can find an easier solution for ya!

3

The STUFF and FOR XML PATH technique is indeed a powerful method for string aggregation. It works by leveraging XML functionality to concatenate values. The inner SELECT creates a comma-separated list of names, which is then wrapped in XML tags. The FOR XML PATH(‘’) part ensures no additional XML elements are created. STUFF is used to remove the leading comma.

While effective, this approach can be complex and potentially impact performance on large datasets. As mentioned, STRING_AGG is a more straightforward alternative in newer SQL Server versions (2017+). For older versions, consider using a recursive CTE or a user-defined aggregate function for better readability and potentially improved performance.

4

yo sophia, that query’s slick! STUFF chops off the first comma while FOR XML PATH consolidates ur names into one string. it’s magic, yeah? string_agg is simpler if available. what version r u on? maybe suggest somethin’ cooler!