Query Cost - Mailing list pgsql-general

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

Thanks for your assistance.

Chris.