On Thu, 18 Apr 2002 [EMAIL PROTECTED] wrote:
>
> On 04/17/2002 01:44:46 PM Michael Loftis wrote:
> > In many of the cases where it is a primary key it is also there to
> > ensure fast lookups when referenced as a foreign key. Or for joins.
>
> Don't know if the optimizer takes this into consideration, but a query that uses a
>primary and/or unique key in the where-clause, should always choose to use
> the related indices (assuming the table size is above a certain threshold). Since a
>primary key/unique index always restricts the resultset to a single row.....
I don't think so.
eg. table with primary key "pk", taking values from 1 to 1000000 (so
1000000 records)
select * from table where pk > 5
should probably not use the index ...
Cheers
Tycho
--
Tycho Fruru [EMAIL PROTECTED]
"Prediction is extremely difficult. Especially about the future."
- Niels Bohr
---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
(send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
