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RE: [HACKERS] Re: [QUESTIONS] Practical SQL Handbook - demo script for postgreSQL

From: "Jackson, DeJuan" <djackson(at)cpsgroup(dot)com>
To: "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu>, Bruce Stephens <bruce(at)cenderis(dot)demon(dot)co(dot)uk>
Cc: The Hermit Hacker <scrappy(at)hub(dot)org>, pgsql-hackers(at)postgreSQL(dot)org
Subject: RE: [HACKERS] Re: [QUESTIONS] Practical SQL Handbook - demo script for postgreSQL
Date: 1998-04-27 17:34:53
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
> > > > The NULL contraint: PostgreSQL only allows NOT NULL (NULL being 
> > > > the default).  I altered the backend grammar for this one.
> > >
> > >       Patch?
> > 
> > OK.  The patch to gram.y is almost certainly wrong: it's just a hack
> > to get NULL acceptable---it should surely go in the same place as
> the
> > check for NOT NULL.
> Yes, and no. Putting the grammar where you did disallows any other
> clauses, such as DEFAULT or CONSTRAINT, in the declaration. Trying to
> put it in the proper place results in shift/reduce conflicts, since it
> is ambiguous with other allowed syntax.
> btw, afaik this is not SQL92 anyway...
> > The floating point literal change is probably right, but it may
> break
> > things (it may well cause more things to be regarded as floats than
> > should be).  Again, somebody who knows about this stuff definitely
> > needs to check.
> > 
> > I hope this helps all the same.
> Yes it does! I've got a more general floating patch to apply, but
> would
> not have done it without your prompting. Discussion and proposals are
> how we progress. Good work.
> Don't know how or if we want to proceed with a bare "NULL" clause.
> Should we bother with a special case of _only_ NULL in a declaration,
> as
> in Bruce's patch?
Continuing with the discussion/proposal theme:  I vote yes for the bare
NULL if it can be done with a minimum of hassle.  It would at the very
least improve compatibility with SYBASE AND MS SQL Server.  I know that
these aren't goals, but it doesn't hurt to have it happen.  Could
someone check the Create table syntax and see if it's SQL92 (I have a
suspicion that it is).

I'm not sure about the 'shift/reduce', but couldn't you interpret the
NULL not preceded by NOT in a CREATE TABLE /ALTER TABLE as an empty
string.  I'm assuming here that the NOT NULL is treated as one token in
the grammar/parser.


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