Postgresql Sequences

Create a new sequence:
CREATE SEQUENCE mytable_myid_seq;

Add the sequence as the incrementor for a table column:
ALTER TABLE mytable
ALTER COLUMN myid
SET DEFAULT NEXTVAL('mytable_myid_seq');

Update existing rows in table with the sequence:
UPDATE mytable
SET myid = NEXTVAL('mytable_myid_seq');

Display the sequence information:
Select * from mytable_myid_seq;

Update a sequence to be one greater than a table's id column:
select setval('mytable_myid_seq', (select max(id) + 1 from mytable));
http://railspikes.com/2009/3/6/duplicate-key-violates-unique-constraint (thanks Louis)
http://pointbeing.net/weblog/2008/03/mysql-versus-postgresql-adding-an-auto-increment-column-to-a-table.html