Adding foreign key constraint post table creation

All,

A couple of novice questions:


I would like to modify an existing TABLE by addinga new column (FOREIGN
KEY): 
      type_id int not null,      foreign key (type_id) references cvterm (cvterm_id),


Will this work ( running PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled
by GCC 2.96):

ALTER TABLE contig ADD COLUMN type_id int;

ALTER TABLE contig ADD CONSTRAINT cvtermfk FOREIGN KEY (type_id)
references cvterm (cvterm_id);
********

I would like to load data into the table below from a file lacking the
timestamp fields, where the file structure is:


COPY table FROM STDIN;
1	feature_type	types of features	\N
2	3'-exon	\N	1 
.
.
.
\.

This fails as the timestamp fields are 'not null'.  Othere than
generating INSERT stmts for the data how else could I enter the data?

create table cvterm (cvterm_id serial not null,primary key (cvterm_id),termname varchar(255) not null,termdefinition text,termtype_id int,foreign key (termtype_id) references cvterm (cvterm_id),timeentered timestamp not null default current_timestamp,timelastmod timestamp not null default current_timestamp,unique(termname, termtype_id)
);


regards,

Charles