pg.ddx.io pgsql-sql@postgresql.org mailing list archive
help / color / mirror / Atom feedcartesian product
4+ messages / 3 participants
[nested] [flat]
* cartesian product
@ 2007-02-19 16:58 Salman Tahir <salmantahir1@gmail.com>
0 siblings, 3 replies; 4+ messages in thread
From: Salman Tahir @ 2007-02-19 16:58 UTC (permalink / raw)
To: pgsql-sql
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
Any help would be appreciated.
- Salman
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: cartesian product
@ 2007-02-19 17:56 Luiz K. Matsumura <luiz@planit.com.br>
parent: Salman Tahir <salmantahir1@gmail.com>
2 siblings, 0 replies; 4+ messages in thread
From: Luiz K. Matsumura @ 2007-02-19 17:56 UTC (permalink / raw)
To: Salman Tahir <salmantahir1@gmail.com>; +Cc: pgsql-sql
Hi, Salman
Maybe this isn't so much elegant, but works:
SELECT p1.sequence as sequence1, p2.sequence as sequence2
FROM potential_pairs p1, potential_pairs p2
WHERE p1.sequence <= p2.sequence
Hope this helps
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
>
> Any help would be appreciated.
>
> - Salman
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match
>
>
--
Luiz K. Matsumura
Plan IT Tecnologia Informática Ltda.
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: cartesian product
@ 2007-02-19 18:07 Scott Marlowe <smarlowe@g2switchworks.com>
parent: Salman Tahir <salmantahir1@gmail.com>
2 siblings, 0 replies; 4+ messages in thread
From: Scott Marlowe @ 2007-02-19 18:07 UTC (permalink / raw)
To: Salman Tahir <salmantahir1@gmail.com>; +Cc: pgsql-sql
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
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: cartesian product
@ 2007-02-19 18:09 Scott Marlowe <smarlowe@g2switchworks.com>
parent: Salman Tahir <salmantahir1@gmail.com>
2 siblings, 0 replies; 4+ messages in thread
From: Scott Marlowe @ 2007-02-19 18:09 UTC (permalink / raw)
To: Salman Tahir <salmantahir1@gmail.com>; +Cc: pgsql-sql
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
Oh wait, slightly different thing you meant. OK, you'll want something
like:
select p1.sequence as sequence1, p2.sequence as sequence2 from
potential_pairs p1, potential_pairs p2 where p1.sequence >= p2.sequence
^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2007-02-19 18:09 UTC | newest]
Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2007-02-19 16:58 cartesian product Salman Tahir <salmantahir1@gmail.com>
2007-02-19 17:56 ` Luiz K. Matsumura <luiz@planit.com.br>
2007-02-19 18:07 ` Scott Marlowe <smarlowe@g2switchworks.com>
2007-02-19 18:09 ` Scott Marlowe <smarlowe@g2switchworks.com>
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox