Hi Svetlana!
I think this is a nice introductory tutorial on using rCTEs.
However like a couple of folks that have already replied, I'd do it a little differently:
WITH Offices AS (
SELECT a.OfficeID, c.StateAbbr, c.CountyName, c.CountyID
FROM Office a
INNER JOIN OfficeCounty b ON a.OfficeID = b.OfficeID
INNER JOIN County c ON b.CountyID = c.CountyID)
SELECT a.OfficeID, StateAbbr=MAX(StateAbbr)
,countynames=STUFF((
SELECT ', ' + CountyName
FROM Offices b
WHERE a.OfficeID = b.OfficeID
ORDER BY CountyName
FOR XML PATH('')), 1, 2, '')
FROM Offices a
GROUP BY a.OfficeID
I believe that the looping string concatenation you're doing in the rCTE will impact your performance vs. something like the above.
To each his (or her) own I suppose.
My thought question: Have you ever been told that your query runs too fast?
My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.
Need to UNPIVOT? Why not CROSS APPLY VALUES instead?[/url]
Since random numbers are too important to be left to chance, let's generate some![/url]
Learn to understand recursive CTEs by example.[/url]
[url url=http://www.sqlservercentral.com/articles/St