Re: foreign key to the *same* table?

From: Leandro Guimarães Faria Corsetti Dutra <lgcdutra_at_terra.com.br>
Date: Sat, 13 Sep 2003 11:24:40 +0200
Message-ID: <pan.2003.09.13.09.24.39.694131@terra.com.br>

On Wed, 10 Sep 2003 00:05:46 +0200, Marco wrote:

> MySQL let me create the
> table and insert records, but problem begins with the clause ON DELETE SET
> NULL
First, beware of MySQL -- it is not ISO SQL compliant, it has lotsa arbitrary restrictions. PostgreSQL is just as cheap, and much better.

Second, think again... any solution involving NULLs is suspect. A nice, reationally sane solution to the hierarchy problem has been proposed by Fabian Pascal in his latest book, and it is a pearl of simplicity: simply a separate binary relation with the relationship between hierarchy nodes; for it, suffices two foreign keys to the main node relation.

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Received on Sat Sep 13 2003 - 04:24:40 CDT