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From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>
To: pgsql-sql@postgresql.org
Subject: Existential quantifier
Date: Sat, 10 Oct 2009 00:53:47 +0200
Message-ID: <86bpkgqiv8.fsf@ds4.des.no>
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Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

Consider the attached schema (filmstars.sql), which is a poorly designed
database of films and actors.  The following query gives me a list of
films in which either Charlie or Martin Sheen starred:

select fs.film.title, fs.film.year
  from fs.film left join fs.star on fs.film.id =3D fs.star.film
  where fs.star.last =3D 'Sheen'
  group by fs.film.title, fs.film.year;

Is there a way to do this without the "group by" clause?

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no


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Content-Disposition: inline; filename=filmstars.sql

drop schema fs cascade;

create schema fs;

create table fs.film (
  id serial not null primary key,
  title varchar not null unique,
  year integer not null
);

create table fs.star (
  id serial not null primary key,
  film integer not null references fs.film(id),
  last varchar not null,
  first varchar not null,
  unique (film, last, first)
);

insert into fs.film(title, year) values ('Apocalypse Now', 1979);
insert into fs.star(film, last, first)
  select id, 'Sheen', 'Martin' from fs.film where title = 'Apocalypse Now';
insert into fs.star(film, last, first)
  select id, 'Brando', 'Marlon' from fs.film where title = 'Apocalypse Now';
insert into fs.star(film, last, first)
  select id, 'Duvall', 'Robert' from fs.film where title = 'Apocalypse Now';
insert into fs.star(film, last, first)
  select id, 'Ford', 'Harrison' from fs.film where title = 'Apocalypse Now';

insert into fs.film(title, year) values ('Blade Runner', 1982);
insert into fs.star(film, last, first)
  select id, 'Ford', 'Harrison' from fs.film where title = 'Blade Runner';
insert into fs.star(film, last, first)
  select id, 'Young', 'Sean' from fs.film where title = 'Blade Runner';
insert into fs.star(film, last, first)
  select id, 'Hauer', 'Rutger' from fs.film where title = 'Blade Runner';
insert into fs.star(film, last, first)
  select id, 'Hannah', 'Daryl' from fs.film where title = 'Blade Runner';

insert into fs.film(title, year) values ('Platoon', 1986);
insert into fs.star(film, last, first)
  select id, 'Sheen', 'Charlie' from fs.film where title = 'Platoon';
insert into fs.star(film, last, first)
  select id, 'Dafoe', 'Willem' from fs.film where title = 'Platoon';
insert into fs.star(film, last, first)
  select id, 'Berenger', 'Tom' from fs.film where title = 'Platoon';

insert into fs.film(title, year) values ('Wall Street', 1987);
insert into fs.star(film, last, first)
  select id, 'Douglas', 'Michael' from fs.film where title = 'Wall Street';
insert into fs.star(film, last, first)
  select id, 'Sheen', 'Charlie' from fs.film where title = 'Wall Street';
insert into fs.star(film, last, first)
  select id, 'Hannah', 'Daryl' from fs.film where title = 'Wall Street';
insert into fs.star(film, last, first)
  select id, 'Sheen', 'Martin' from fs.film where title = 'Wall Street';

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