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Re: [HACKERS] Re: NULL & NOT NULL

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu>
Cc: Postgres Hackers List <hackers(at)postgreSQL(dot)org>
Subject: Re: [HACKERS] Re: NULL & NOT NULL
Date: 1998-12-24 14:33:18
Message-ID: 4895.914509998@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Thomas G. Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu> writes:
>>>>>> create table authors (
>>>>>> zip             char(5)         null
>>>>>> );

> Sheesh. After that long song and dance about why we can't implement
> this, it turns out that it works fine. We had been trying to implement a
> slightly different syntax, "WITH NULL", which conflicted with the
> SQL92-defined data type declaration "TIMESTAMP WITH TIME ZONE".

> The "Practical SQL Handbook"-compatible form will be available in the
> next full release of Postgres. Thanks.

Now that we have the syntax problem straightened out: I'm still confused
about the semantics.  Does a "NULL" constraint say that the field
*must* be null, or only that it *can* be null (in which case NULL is
just a noise word, since that's the default condition)?  I had assumed
the former, but Bruce seemed to think the latter...

			regards, tom lane

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Next:From: Bruce MomjianDate: 1998-12-24 15:47:27
Subject: Re: [HACKERS] Re: NULL & NOT NULL
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Subject: Re: NULL & NOT NULL

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