mickyT (7/1/2013)
HiA while back I got told by someone to avoid using additional functions on the XML if possible as they can have a big impact on the performance.
For example on my machine this
SELECT @CaseID=CaseID, @Name=Name,@PrimaryCodes=STUFF((
SELECT ',' + CaseCode
FROM #CaseCode b
WHERE a.CaseID = b.CaseID AND b.TypeFlag = 'P'
ORDER BY CaseCode
FOR XML PATH('')), 1, 1, '')
,@SecondaryCodes=STUFF((
SELECT ',' + CaseCode
FROM #CaseCode b
WHERE a.CaseID = b.CaseID AND b.TypeFlag = 'S'
ORDER BY CaseCode
FOR XML PATH('')), 1, 1, '')
FROM #Case a
runs in 11 secs rather than 34 secs. Looking at the plans for the different queries, the one above does not use a XML Reader
A very interesting point Micky! I used it for compatibility with what Luis had done. But if you don't need it because you're sure there are no special characters in the CaseCodes, then by all means do without it.
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