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From: jose soares <jose@sferacarta.com>
To: Bruce Stephens <bruce@cenderis.demon.co.uk>
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] NULL
Date: Tue, 16 Nov 1999 14:37:05 +0100
Message-ID: <38315E00.4CDB885F@sferacarta.com> (raw)
References: <383059DA.9D2AF70D@kirra.net>
	<87u2mnttmt.fsf@cenderis.demon.co.uk>

Bruce Stephens ha scritto:

> Goran Thyni <goran@kirra.net> writes:
>
> > How about this according to SQL standard:
> >
> > CREATE TABLE x { y integer NULL };
> >
> > It suppose to mean that NULLs are explicitly allowed in
> > this field.
> > Is this required by SQL-92?
>
> No, it's not required.  This came up before with the examples from
> "The Practical SQL Handbook".  It would be nice to allow it, but there
> was some reason why to do so would be non-trivial, which I forget.
> Anyway, it's not in SQL-92.
>
> ************

Sorry, I don't understand why we need this feature. This is completely out
of standard.

What's that mean ?

-  Is it a constraint to allow only NULL values ?  (unuseful)

- If this is a default value we already have this in:
  CREATE TABLE  table1 (field1  int DEFAULT NULL);

- According with SQL-92 every column can store a NULL value by default
  unless one specify a NOT NULL constraint for the column.

José

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