Type:  \copyright for distribution terms
      \h for help with SQL commands
      \? for help with psql commands
      \g or terminate with semicolon to execute query
      \q to quit

postgres=# CREATE TABLE Actor (id integer, name varchar(32));
CREATE TABLE
postgres=# select * from Actor;
 id | name
----+------
(0 rows)

postgres=# insert into Actor (id,name) values (1,'HHG');
INSERT 0 1
postgres=# select * from Actor;
 id | name
----+------
 1 | HHG
(1 row)

postgres=# create table Movie (id integer, title varchar(32));
CREATE TABLE
postgres=# insert into Movie (id, title) values (1, 'A');
INSERT 0 1
postgres=# insert into Movie (id, title) values (2, 'B');
INSERT 0 1
postgres=# insert into Movie (id, title) values (3, 'C');
INSERT 0 1
postgres=# select * from Movie;
 id | title
----+-------
 1 | A
 2 | B
 3 | C
(3 rows)

postgres=# create table Role (aid integer, mid integer);
CREATE TABLE
postgres=# insert into Role (aid, mid) values (1,2);
INSERT 0 1
postgres=# select * from Role;
 aid | mid
-----+-----
  1 |   2
(1 row)

postgres=# insert into Role (aid, mid) values (2,2);
INSERT 0 1
postgres=# insert into Actor (id,name) values (2, 'X');
INSERT 0 1
postgres=# select * from Role where mid=2;
 aid | mid
-----+-----
  1 |   2
  2 |   2
(2 rows)

postgres=# select * from Role where mid=3;
 aid | mid
-----+-----
(0 rows)

postgres=# select * from Role where mid=2;
 aid | mid
-----+-----
  1 |   2
  2 |   2
(2 rows)

postgres=# select a.name from Role r, Actor a where r.aid=a.id and r.mid=2;
 name
------
 HHG
 X
(2 rows)