On 2001-06-26 at 21:45 +0200, [EMAIL PROTECTED] wrote:
> On Tue, Jun 26, 2001 at 10:04:15AM -0700, kenneth wrote:
>
> > 2. A sophisticated database will optimize it's use of a disk, especially a
> > SCSI disk, and lay records down in such a way that the heads insert/read
> > sequential data very efficiently. 'Random' keys will checkerboard your data.
>
> Why would this matter? Do databases assume that records with primary
> keys "near" one another will often be used together?
Yes, this is why they are called "primary keys." Traditionally, database
engines would try to entry-sequence records by primary key, and there
remains an expectation that access by primary key will always be the
fastest and most efficient mechanism for accessing a table.
-- Mike
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