From: Viorel Dragomir <bigchief@vio.ro>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-sql@postgresql.org
Subject: Re: summing tables
Date: Tue, 15 Jul 2003 18:49:40 +0300
Message-ID: <016101c34ae8$b4277a20$0600a8c0@fix.ro> (raw)
References: <20030715140921.7c5a6a6c.erik@thiele-hydraulik.de>
<001501c34aca$e70ca280$0600a8c0@fix.ro>
<20030715143925.54716ed4.erik@thiele-hydraulik.de>
<22671.1058282096@sss.pgh.pa.us>
<012b01c34ae6$40ab0870$0600a8c0@fix.ro>
<22931.1058283723@sss.pgh.pa.us>
----- Original Message -----
From: "Tom Lane" <tgl@sss.pgh.pa.us>
To: "Viorel Dragomir" <bigchief@vio.ro>
Cc: <pgsql-sql@postgresql.org>
Sent: Tuesday, July 15, 2003 6:42 PM
Subject: Re: [SQL] summing tables
> "Viorel Dragomir" <bigchief@vio.ro> writes:
> > Indeed it was a mistake not to put the table_name. in where clause.
> > But this doesn't resolve the problem.
>
> > Do you know in which order the update will modify the rows?
>
> No, and *it does not matter*. You are forgetting that this all runs
> under MVCC rules. The sub-SELECTs will see the pre-existing versions
> of the rows, whether or not the UPDATE has yet produced new versions.
Yes that was correct.
I forgot that the subselect sees only the old rows.
And the ORDER option will not make any difference, only making fool out of
myself. :)
I don't know if the problem is solved with my posted function.
Anyway this is the mail that started all [i get a lot of emails and i'm not
really searching for a solution on this matter]:
"
hi,
i have a table consisting of 4 integers.
seq is for making the table ordered. (ORDER BY SEQ ASC)
a,b,c maybe null
seq | a | b | c
-----+----+----+---
0 | 1 | 2 | 3
1 | 1 | 2 |
2 | 5 | 7 |
3 | -2 | -4 |
i am needing a sql statement to do
c=a+b+"the c of the row with seq one less than myself"
this statement has to run over the whole table, in seq order.
how can this be acomplished???
cu&thanks
erik
--
Erik Thiele
"
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To: pgsql-sql@postgresql.org
Cc: bigchief@vio.ro, tgl@sss.pgh.pa.us
Subject: Re: summing tables
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