in reply to Which data structure should I use?

You said ID isn't unique, and you said ID is unique. Which one is it? It's a crucial detail in determining the answer.

(Answered over here as I was typing)

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Re^2: Which data structure should I use?
by Anonymous Monk on Sep 06, 2009 at 23:39 UTC
    Yes, my mistake...
    The format is as you see it, that is ID is UNIQUE, while FIRST_NUMBER and SECOND_NUMBER are not unique...