murgatroid (1/30/2013)
This is very nearly the same type of problem discussed in Phil Factor's SQL Speed Phreak challenge http://ask.sqlservercentral.com/questions/1227/the-subscription-list-sql-problem.html, which is also discussed nicely here http://www.simple-talk.com/sql/performance/writing-efficient-sql-set-based-speed-phreakery/. Besides being a good read, I think that you could use the winning code easily enough, substituting days for months and guests for subscribers.
Heavens to murgatroid!
I'd seen that article and forgotten about it. Thanks for reminding me.
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]
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