Adding PK to Existing Table

   In -9.0.3 I used ALTER TABLE to replace a varchar() column with a bigint
column so it can be assigned as the table's primary key. From the 9.0.3
manual I tried various flavors of ALTER TABLE <tablename> ADD CONSTRAINT but
cannot find the proper syntax to create the PK. Do I need to first make the
column UNIQUE, then add a NOT NULL constraint?

Rich