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CTEs Don’t Control Plan Shape

Erik Darling dispels a myth:

I’ve heard many times incorrectly over the years that CTEs somehow materialize data.

But a new one to me was that CTEs execute procedurally, and you could use that to influence plan shapes by always doing certain things first.

Unfortunately, that’s not true of them either, even when you use TOP.

Read the whole thing. Though I do chain common table expressions for readability’s sake, but that’s usually because I’m performing a series of repetitive calculations that I can’t simplify via APPLY.

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