sequences/operators

Hello.

I have declared a sequence for assigning invoice numbers.

When I first began inserting the number from the sequence into tables,
there was some message regarding int4. So the simplest solution seemed to
be to change the type for "inv_no" to int4.

My first question is whether there is an alternative approach which would
allow me to define "inv_no" as a simple int.

Currently I can insert into the table invoices, but when I try a select:

SELECT * FROM invoices WHERE inv_no = '10074';

I get:

caxton=> select * from order_details where inv_no = '10074';
NOTICE:there is more than one operator = for types
NOTICE:int4 and unknown. You will have to retype this query
WARN:using an explicit cast

And then with:

SELECT * FROM invoices WHERE inv_no == '10074';

I get:

NOTICE:there is no operator == for types int4 and unknown
NOTICE:You will either have to retype this query using an
NOTICE:explicit cast, or you will have to define the operator
WARN:== for int4 and unknown using CREATE OPERATOR

If anyone could clarify what's going on here, and what the simplest
solution may be, I would certainly appreciate it!

Great thanks in advance,

Os