Re: Problems with SELECT *

"Cimarron Taylor" <cimarron+google_at_taylors.org> wrote in message news:29e28c51.0303131009.10514345_at_posting.google.com...
> > Databases physically store data in an atomic page of information:
> > data page or block. Within the block, as many rows are stored as
> > possible. When a SELECT is done, the data page/block is read into
> > the
> > 'buffer cache' Whether you do SELECT * or SELECT userid, all the
> > data
> > is in the buffer cache.
>
> Not if the system is column-oriented or if the table uses
> a "Vertical Partitioning" scheme.

Another thing is that some system, provided there's an index, may "cover" the query fetching densely populated index pages instead of fetching the data pages.

Gianluca Hotz. Received on Fri Mar 14 2003 - 14:12:51 CET