On Sun, Sep 18, 2005 at 07:40:26PM +0100, ShepherdHill DB Subscriptions wrote:
> Hi,
>
> I have a table with this schema:
>
> CREATE TABLE billing.bill
> (
> sno serial NOT NULL,
> billno int4,
> det date NOT NULL,
> .
> .
> .
> CONSTRAINT bill_pkey PRIMARY KEY (sno)
> )
>
> I want to execute a query that will not return any record. Which of
> these queries is cheaper please?
>
> 1. Select * from billing.bill where 1=0
> 2. Select * from billing.bill where sno=0
Do an explain analyze and see. :)
1 will be faster because the optimizer can discard it right off the bat.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461