From: Rod Taylor <pg@rbt.ca>
To: David Garamond <lists@zara.6.isreserved.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Displaying two tables side by side
Date: Wed, 11 Aug 2004 14:32:30 -0400
Message-ID: <1092249149.16087.28.camel@jester> (raw)
In-Reply-To: <411A2926.9020500@zara.6.isreserved.com>
References: <411A2926.9020500@zara.6.isreserved.com>
Depending on the size of your structures, something like the below may
be significantly faster than the subselect alternative, and more
reliable than the ctid alternative.
CREATE TYPE result_info AS (a integer, b integer, c integer, d integer);
CREATE OR REPLACE FUNCTION parallelselect() RETURNS SETOF result_info AS
'
DECLARE
res result_info%rowtype;
ct1_found boolean DEFAULT true;
ct2_found boolean DEFAULT true;
ct1 CURSOR FOR SELECT a,b FROM t1;
ct2 CURSOR FOR SELECT c,d FROM t2;
BEGIN
OPEN ct1;
OPEN ct2;
LOOP
FETCH ct1 INTO res.a, res.b;
ct1_found := FOUND;
FETCH ct2 INTO res.c, res.d;
ct2_found := FOUND;
IF ct1_found OR ct2_found THEN
RETURN NEXT res;
ELSE
EXIT;
END IF;
END LOOP;
RETURN;
END;
' LANGUAGE plpgsql;
SELECT * FROM parallelselect() AS tab;
a | b | c | d
---+---+---+---
2 | 2 | 4 | 5
3 | 5 | 7 | 3
4 | 7 | 3 | 2
9 | 0 | 1 | 1
| | 2 | 0
(5 rows)
On Wed, 2004-08-11 at 10:11, David Garamond wrote:
> How can you display two tables side by side? Example:
>
> > select * from t1;
> a | b
> ---+---
> 2 | 2
> 3 | 5
> 4 | 7
> 9 | 0
>
> > select * from t2;
> c | d
> ---+---
> 4 | 5
> 7 | 3
> 3 | 2
> 1 | 1
> 2 | 0
>
> Intended output:
> a | b | c | d
> ---+---+---+---
> 2 | 2 | 4 | 5
> 3 | 5 | 7 | 3
> 4 | 7 | 3 | 2
> 9 | 0 | 1 | 1
> | | 2 | 0
>
> Each table has no keys (and no OIDs). Order is not important, but each
> row from each table needs to be displayed exactly once.
>
> --
> dave
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
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To: pgsql-sql@postgresql.org
Cc: pg@rbt.ca, lists@zara.6.isreserved.com
Subject: Re: Displaying two tables side by side
In-Reply-To: <1092249149.16087.28.camel@jester>
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