sequence primary key

Hi all,

my question is about sequences and primary key of a table.
More details : I create a sequence and a table with these lines :

CREATE SEQUENCE "my_id" INCREMENT 1 MINVALUE 1 MAXVALUE 2147483647 START 1
CACHE 1;

CREATE TABLE "toto" (
    "toto_id" integer PRIMARY KEY DEFAULT nextval('"my_id"'),
    "db" text);

in a a sql file.
In fact, when I fill database I would like "toto_id" field to be filled
directly by sgdb by using sequence "my_id" but not by me.
This way doesn't work. It's perhaps a big mistake !!!
How is-it possible, so ?
Thanks a lot.

Virginie.