Re: [OT] "advanced" database design (long)

Em Monday 04 February 2008 07:03:47 Dawid Kuroczko escreveu:
> On Feb 4, 2008 5:14 AM, Alex Turner <armtuk@gmail.com> wrote:
> > I"m not a database expert, but wouldn't
>
> [...]
>
> > give you a lot less  pages to load than building a table with say 90
> > columns in it that are all null, which would result in better rather than
> > worse performance?
>
> Well, but PostgreSQL's NULLs occupy almost no space, or rather a bit of
> space, that is one bit exactly. ;-)  I am pretty much sure that
> storage-wise looking NULLs
> are more efficient.

I'd say 1 byte every 8 NULLs instead of 1 bit.  If you only have 1 NULL, it
will cost you 1 byte (not 1 bit).  If you have 9, it will cost you 2 bytes
(not 9 bits).

--
Jorge Godoy      <jgodoy@gmail.com>