From: Peter Eisentraut <peter_e@gmx.net>
To: Rod Taylor <pg@rbt.ca>
Subject: Re: ENUM like data type
Date: Wed, 29 Jun 2005 23:20:32 +0200
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Rod Taylor wrote:
> Indeed. A CHECK constraint on a DOMAIN is an ENUM plus some.

Not really.  A domain doesn't create a new type.  If you base your enum 
domains on the text type, as would usually be the case, then nothing 
stops you from using, say, text concatenation operators and the like.  
I suppose in practice this won't matter too much, but it can't be 
called a clean design.  What you'd really need is a way to create a 
distinct type.  SQL has a feature for that, but PostgreSQL hasn't 
implemented it.

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/