Re: Is CREATE TYPE an alias for CREATE DOMAIN?

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От Bruce Momjian
Тема Re: Is CREATE TYPE an alias for CREATE DOMAIN?
Дата
Msg-id 200512221613.jBMGDUx09493@candle.pha.pa.us
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Ответ на Re: Is CREATE TYPE an alias for CREATE DOMAIN?  ("Jim C. Nasby" <jnasby@pervasive.com>)
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Jim C. Nasby wrote:
> On Thu, Dec 22, 2005 at 09:36:52AM +0000, Richard Huxton wrote:
> > John Dean wrote:
> > >Hi
> > >
> > >Could somebody please tell me if CREATE TYPE is equivalent to CREATE
> > >DOMAIN? If not is there a work around
> >
> > What do you mean by "equivalent"? You wouldn't use them in the same way,
> > and I'm not sure what a work-around would consist of.
> >
> > What are you trying to do?
>
> Some (most?) database's idea of 'creating a type' is actually what we
> consider creating a domain, since many databases don't support users
> adding arbitrary types to the system. I suspect this user is trying to
> port some code over...

CREATE DOMAIN builds on an existing data type and adds additional
characteristics and checks to the type.  It is sort of like a macro for
types.

CREATE TYPE creates a new data type, independent of existing data types,
and usually requires C code and a shared object file to load into the
database.

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