2 novice questions

Do primary keys need to be defined in all tables that are releated by the
key or only in the primary one?

For instance if I create tables to hold file info as shown below...

CREATE TABLE filename (id SEQUENCE PRIMARY KEY, name TEXT UNIQUE);

CREATE TABLE filestat (id INTEGER, size INTEGER, ts TIMESTAMP, md5
CHAR(32));

Does the filestat.id column need a PRIMARY KEY constraint?

Also, if I have a read only user, do I need to grant SELECT access on the
sequence?
GRANT SELECT ON filename_id_seq TO myuser;

Thanks for all the help this list provides:)

Thanks,

dale(dot)sykora(at)compaq(dot)com