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php-db | 2001011

Re: [PHP-DB] ENUM type From: Alexey Borzov (borz_off <email protected>)
Date: 01/15/01

Greetings, Cahyo!

At 15.01.01, 18:47, you wrote:
CSA> I don't know what is the benefit if we use ENUM type.
CSA> can everybody explain it?

It is an ugly crutch.

Well, you see, most RDBMSes will allow you to make a 'lookup
table' or 'dictionary' or something (dunno its official name).

Something like:

CREATE TABLE foo_baz_dictionary (
  baz integer not null primary key,
  baz_name char(50)
);

-- baz is a potential "enum" field
CREATE TABLE foo (
  bar integer,
  ...
  baz integer,
  foreign key (baz) references foo_baz_dictionary
);

Then when you insert something into 'foo', its 'baz' field is checked
against foo_baz_dictionary (which is far more manageable
than ENUM field definition).

MySQL does not support foreign keys and so its creators came up with ENUM
solution. 

-- 
Yours, Alexey V. Borzov, Webmaster of RDW

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