Marco Russo and Alberto Ferrari observe the dog that didn’t bark:
What products did not sell in a specific area, store, or time period? This may be an important analysis for several businesses. There are multiple ways to obtain the desired result. Some specific implementations might be needed because of the user or model requirements, whereas developers can choose any formula in several cases. Or you might just find a solution on the web and blindly implement it without questioning whether there is a better way to achieve what you want.
It turns out that different formulas perform very differently. Choosing the right one in your scenario can make a slow report fast. This article analyzes the performance of different formulations of one same algorithm.
It’s interesting to see the performance profile here: most are reasonably close together, although you can still get a 2x gain from using the fastest approach versus the second-slowest. And then there’s the slowpoke.