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Re: [HACKERS] Re: NULL & NOT NULL

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: tgl(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane)
Cc: lockhart(at)alumni(dot)caltech(dot)edu, hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Re: NULL & NOT NULL
Date: 1998-12-24 15:47:27
Message-ID: 199812241548.KAA19292@candle.pha.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...


Can be null.  Noise word.  At least that is what I rememeber Thomas
saying, and because it was noise, we removed it.  In fact, it doesn't
look like the standard accepts it, but there is no reason we can't.

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  maillist(at)candle(dot)pha(dot)pa(dot)us            |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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