Show calculated results on the fly vs. Storing pre-calculated results in a table

I have results that are calculated from multiple rows in many different tables. These results are then displayed in a profile. To show the most current results on request, should i store these results in a separate table and upda开发者_如何学Gote them on change? or should i go with calculating these results on the fly?

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As usual with performance questions, the answer is "it depends".

I'd probably start by calculating the results on the fly and go with precomputing them when it starts to be a problem.

If you have precomputed/summarized copies of your main data, you'll have to set up an updating process to make sure your summaries are correct. This can be quite tricky and can add a lot of complexity to your application so I wouldn't do it unless I had to. You'll also want to have a set of sanity check tools to make sure your summaries are, in fact, correct. And a set of "kill it all and rebuild the generated summaries" tools will also come in handy.

If these calculations are a problem (and by that I mean that you have measured the performance and know that your the queries in question are a bottleneck and you have the numbers to prove it) then it might be worth the extra coding and maintenance effort.