Jeff Moden (10/24/2010)
For the simple task of sorting in the correct order, we'll use the "Hierarchical Path" method. To build it, we'll use a "Recursive CTE". Look that up in Books Online for a better understanding of them. I will tell you right now that they are NOT a panacea. Hierarchies are one of the few places where I don't mind the use of recursive CTE's because they're normally RBAR code. In the example that follows, the recursive CTE is "layered" or (as Celko calls it), "lasagna" code. It processes a full set (one full level) of information for each iteration which makes it non-RBAR code. It's still a bit slower than a more lengthy method but it takes a huge hierarchy to really appreciate the difference so the recursive CTE is usually good enough.
Oh my! No fair! I love posting recursive CTE solutions and you beat me to 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]
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