From: | "Andrew L(dot) Gould" <algould(at)datawok(dot)com> |
---|---|
To: | Ron Johnson <ron(dot)l(dot)johnson(at)cox(dot)net>, PgSQL General ML <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Arrays and "goodness" in RDBMSs (was Re: join of array) |
Date: | 2003-08-15 18:37:50 |
Message-ID: | 200308151337.50591.algould@datawok.com |
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Lists: | pgsql-general pgsql-patches |
On Friday 15 August 2003 01:13 pm, Ron Johnson wrote:
> On Fri, 2003-08-15 at 12:41, Joe Conway wrote:
> > Tom Lane wrote:
> > > That's about as clear as mud :-( ... but I found a clearer statement
> > > in SQL99 6.31:
> > >
> > > 2) If <array concatenation> is specified, then:
> > >
> > > a) Let AV1 be the value of <array value expression 1> and let AV2 be
> > > the value of <array value expression 2>.
> > >
> > > b) If either AV1 or AV2 is the null value, then the result of the
> > > <array concatenate function> is the null value.
> > >
> > > c) Otherwise, the result is the array comprising every element of AV1
> > > followed by every element of AV2.
> > >
> > > (c) seems to be pretty clearly what Pavel wants for the 1-D case, but
> > > it's not immediately clear how to apply it to multidimensional
> > > arrays.
> >
> > Thanks -- I found the corresponding paragraph in SQL200x (6.35) and it
> > pretty much reads the same.
>
> Why are arrays even mentioned in the the same breath wrt relations
> DBMSs? Aren't they an anathema to all we know and love?
This gives rise to a couple of good questions:
When and why would you want to use arrays instead of a relational model?
Thanks,
Andrew Gould
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