pgunn=# \d entities
                                    Table "entities"
 Column |          Type          |                      Modifiers                       
--------+------------------------+------------------------------------------------------
 eid    | integer                | not null default nextval('"entities_eid_seq"'::text)
 name   | character varying(120) | 
Primary key: entities_pkey
Unique keys: entities_name_key

pgunn=# \d friends
                             Table "friends"
 Column |  Type   |                      Modifiers                       
--------+---------+------------------------------------------------------
 e1     | integer | not null
 e2     | integer | not null
 rank   | integer | not null default nextval('"friends_rank_seq"'::text)
Unique keys: friends_rank_key

pgunn=# select rank,eid from friends,entities where friends.e1 = entities.eid;