domain feature - details

Hi all:
More details on what domains are. Domains are global
column definitions, upon which column definitions
can be based. A domain specifies a data type, and a
set of column attributes and constraints. Subsequent
table definitions can use the domain to define columns.

Here is the detail for 'ALTER DOMAIN' feature. I
pulled this off the chapter 42 at
http://sunsite.unc.edu/LDP/HOWTO/Database-HOWTO.html

<alter domain statement> ::=
ALTER DOMAIN <domain name> <alter domain action>

<alter domain action> ::=
<set domain default clause>
| <drop domain default clause>
| <add domain constraint definition>
| <drop domain constraint definition>

<set domain default clause> ::= SET <default clause>

<drop domain default clause> ::= DROP DEFAULT

<add domain constraint definition> ::=
ADD <domain constraint>

<drop domain constraint definition> ::=
DROP CONSTRAINT <constraint name>

<drop domain statement> ::=
DROP DOMAIN <domain name> <drop behavior>

And the create domain syntax is as follows:---
<domain definition> ::=
CREATE DOMAIN <domain name>
[ AS ] <data type>
[ <default clause> ]
[ <domain constraint>... ]
[ <collate clause> ]

<domain constraint> ::=
[ <constraint name definition> ]
<check constraint definition> [ <constraint attributes> ]

(To search a word in chapter 42, use CTRL+F in browser)
I hope to see this in postgreSQL 6.4

al
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