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Subject: Re: Existential quantifier
From: Richard Albright <ralbright@insiderscore.com>
To: Dag-Erling =?ISO-8859-1?Q?Sm=F8rgrav?= <des@des.no>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <86bpkgqiv8.fsf@ds4.des.no>
References: <86bpkgqiv8.fsf@ds4.des.no>
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Date: Fri, 09 Oct 2009 19:11:09 -0400
Message-Id: <1255129869.11289.4.camel@indie-desktop>
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you could use distinct on

select distinct on (fs.film.title, fs.film.year ) title, year
from fs.film left join fs.star on fs.film.id = fs.star.film
  where fs.star.last = 'Sheen';

On Sat, 2009-10-10 at 00:53 +0200, Dag-Erling Smørgrav wrote:
> 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 = fs.star.film
>   where fs.star.last = 'Sheen'
>   group by fs.film.title, fs.film.year;
> 
> Is there a way to do this without the "group by" clause?
> 
> DES
> plain text document attachment (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';
-- 
Rick Albright
Senior Quantitative Analyst
Insiderscore LLC
ralbright@insiderscore.com