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Coin combinations Expand / Collapse
Posted Monday, November 25, 2013 12:14 AM

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L' Eomot Inversé (11/23/2013)

The idea of building tuples and then using a splitter to pull them apart looks promising. I am going to have a look and see if I gets me where I want to be, ie in a position to do early pruning for the case where all the joins are necessary because none of the conditions for alternative algorithms are satisfied without losing the ability to cope with a fairly unlimited variable number of denominations. I think I will have to either invent some rules such as no two denominations may be coprime and no denomination can be more than 500 times the smallest denomination, or have a much smaller limits on number of coins, though.

Tom - Your analysis was spot on. I couldn't make it work using the approach I tried.

Looks to me like you've already done a pretty dynamite job with your cascading CTEs. Didn't look in detail at what MM posted above, but yours smokes anything I was able to come up with.

Nice one!

My mantra: No loops! No CURSORs! No RBAR! Hoo-uh!

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?
Since random numbers are too important to be left to chance, let's generate some!
Learn to understand recursive CTEs by example.
Splitting strings based on patterns can be fast!
My temporal SQL musings: Calendar Tables, an Easter SQL, Time Slots and Self-maintaining, Contiguous Effective Dates in Temporal Tables
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