Select at least one from each category?

Question

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I\'ve got an SQLite database with a bunch of test/exam questions. Each question belongs to one question category.

Answer 1

Since it's sqlite (thus local): How slow would it be to just query until you have 5 answers and four different categories, dropping the duplicate category rows each iteration.

I think, if each category is equally represented, that it would be highly unlikely that you need more than 3 iterations which should still be below a second.

It's not algorithmically nice, but to me using random() in a SQL statement isn't algorithmically nice anyway.