From: nha <lyondif02@free.fr>
To: "Gau, Hans-Jürgen" <Hans-Juergen.Gau@LGN.Niedersachsen.de>
Cc: PgSQL-sql <pgsql-sql@postgresql.org>
Subject: Re: WG: sql-porting-problem oracle to postgresql with UPDATE/IS NOT NULL
Date: Wed, 29 Jul 2009 13:03:59 +0200
Message-ID: <4A702C9F.2020306@free.fr> (raw)
In-Reply-To: <4A7022C4.9040802@free.fr>
References: <670F563845D6B34189933C9C7322B4872C089C@LV-MX-00002-V02.LV.ads.niedersachsen.de>
<4A7022C4.9040802@free.fr>
Hello again,
Le 29/07/09 12:21, nha a écrit :
> Hello,
>
> Le 29/07/09 11:48, Gau, Hans-Jürgen a écrit :
>> Sorry, it's a lapse by copying and simplification the original version. that
>> is correct:
>>
>> UPDATE table1 t1
>> SET (t1.id) =
>> (SELECT t3.id FROM table2 t2,table3 t3, table1 t1
>> WHERE t3.field = t2.field
>> AND t2.id = t1.id
>> AND t1.id <> t3.id)
>> WHERE
>> (SELECT t3.id FROM table2 t2,table3 t3, table1 t1
>> WHERE t3.field = t2.field
>> AND t2.id = t1.id
>> AND t1.id <> t3.id) IS NOT NULL;
>> [...]
>> the solution brought by Daryl Richter has no effect.
>
> There is one mistake [...]
To be concrete, a valid version would be:
UPDATE table1 t1
SET id = (something)
WHERE (anotherthing);
> Except this point, the query is valid although I am not sure the result
> is always what you may expect [...]
To "join" table1 column (assumed: id) to the subquery (sub-select here)
expression, table1 recall is not relevant in the subquery. Moreover an
alias "t1" is already defined to table1 (at the beginning of the statement).
A more suitable version would be:
UPDATE table1 t1
SET id = (SELECT t3.id FROM table2 t2, table3 t3
WHERE t3.field = t2.field AND t2.id = t1.id AND t1.id <> t3.id)
WHERE (SELECT t3.id FROM table2 t2, table3 t3
WHERE t3.field = t2.field AND t2.id = t1.id AND t1.id <> t3.id) IS NOT
NULL;
A PostgreSQL-compliant version could also be:
UPDATE table1 t1
SET id = t3.id
FROM table2 t2, table3 t3
WHERE t3.field = t2.field AND t2.id = t1.id AND t1.id <> t3.id AND
t3.id IS NOT NULL;
A PostgreSQL-compliant and faster version may be:
UPDATE table1 t1
SET id = t3.id
FROM table2 t2
INNER JOIN
(SELECT t.id, t.field FROM table3 t WHERE t.id IS NOT NULL) t3
ON t3.field = t2.field
WHERE t2.id = t1.id AND t3.id <> t1.id;
Hoping a satisfying solution is up.
--
nha / Lyon / France.
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To: pgsql-sql@postgresql.org
Cc: lyondif02@free.fr, Hans-Juergen.Gau@LGN.Niedersachsen.de
Subject: Re: WG: sql-porting-problem oracle to postgresql with UPDATE/IS NOT NULL
In-Reply-To: <4A702C9F.2020306@free.fr>
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