1. is there an optimal way to design a database table to represent an tree structure ?
I think there's a good candidate. I have to thank demerphq for drawing my attention to it, a few months ago. Look up Joe Celko's article trees in SQL. There's several copies of this (and a follow-up) article floating around on the internet — some even with user comments; he also wrote an entire book about it.

In reply to Re: Tree Structure and Db by bart
in thread Tree Structure and Db by InfiniteLoop

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