affect vs effect

I consider myself a real idiot when it comes to the English language, and perhaps a lot of other things. Every time I see the DB function affected_rows, it makes me wonder if it should be effected_rows. So I checked it out on Google, and talked to somebody else about it, and it didn't help.

If affect is supposed to be a verb, and effect a noun, but "affected rows" makes it an adjective, right? Nowhere in the dictionary that I'm looking at does it say that affected or effected would be right.