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Re^2: Tree Structure and Db

by simonm (Vicar)
on Jul 06, 2005 at 16:26 UTC ( #472867=note: print w/ replies, xml ) Need Help??


in reply to Re: Tree Structure and Db
in thread Tree Structure and Db

In a tree-wise data structure, with only one parent per child, what is the perceived advantage of using this linking table rather than just adding the parent ID to the main table?


Comment on Re^2: Tree Structure and Db
Re^3: Tree Structure and Db
by SimonClinch (Chaplain) on Jul 07, 2005 at 11:18 UTC
    A link table is the normal way to enforce referential integrity in many to many relationships (0 or 1 counts as many for these purposes) and in this case prevents orphans; it also enables you to define different types of relationship without putting more illegal or awkwardly-implemented constraints (and adding maybe-null foreign keys for them) on the master table.

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