Re: cartesian product
От
Scott Marlowe
Тема
Re: cartesian product
Дата
Msg-id
1171908452.25338.2.camel@state.g2switchworks.com
Ответ на
cartesian product (Salman Tahir)
Список
Дерево обсуждения
cartesian product "Salman Tahir" <salmantahir1@gmail.com>
Re: cartesian product Scott Marlowe <smarlowe@g2switchworks.com>
Re: cartesian product Scott Marlowe <smarlowe@g2switchworks.com>
Re: cartesian product "Luiz K. Matsumura" <luiz@planit.com.br>
On Mon, 2007-02-19 at 10:58, Salman Tahir wrote:
> Hi,
>
> I have a query regarding an SQL statement I'm trying to execute. I
> have the following table:
>
> sequence
> -------------+
> AK
> AKCMK
> CMKA
>
> I execute the following statement (Cartesian product):
>
> SELECT p1.sequence as sequence1, p2.sequence as sequence2
> FROM potential_pairs p1, potential_pairs p2
>
> which gives me:
>
> sequence1 | sequence2
> ----------------+--------------
> AK | AK
> AK | AKCMK
> AK | CMKA
> AKCMK | AK
> AKCMK | AKCMK
> AKCMK | CMKA
> CMKA | AK
> CMKA | AKCMK
> CMKA | CMKA
> (9 rows)
>
> I want to eliminate duplicates and by duplicate I mean a tuple such as
> {AK, CMKA} should be regarded as the same as {CMKA, AK}. So I would
> like the following result:
>
> sequence1 | sequence2
> ----------------+--------------
> AK | AK
> AK | AKCMK
> AK | CMKA
> AKCMK | AKCMK
> AKCMK | CMKA
> CMKA | CMKA
>
SELECT p1.sequence as sequence1, p2.sequence as sequence2 FROM
potential_pairs p1, join potential_pairs p2 on
(p1.sequence<>p2.sequence) where sequence1 > sequence2
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