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Re: Running Update Problem

From: <pankaj_wolfhunter_at_yahoo.co.in>
Date: Mon, 25 Jun 2007 08:08:33 -0700
Message-ID: <1182784113.239019.294370@q69g2000hsb.googlegroups.com>


On Jun 25, 7:16 pm, "Chris L." <diver..._at_uol.com.ar> wrote:
> On 23 jun, 06:03, "pankaj_wolfhun..._at_yahoo.co.in"
>
>
>
>
>
> <pankaj_wolfhun..._at_yahoo.co.in> wrote:
> > On Jun 23, 12:04 am, "Chris L." <diver..._at_uol.com.ar> wrote:
>
> > > On 22 jun, 14:59, "pankaj_wolfhun..._at_yahoo.co.in"
>
> > > <pankaj_wolfhun..._at_yahoo.co.in> wrote:
> > > > Greeting,
>
> > > > I have a table say t1 with structure as (dummy)
>
> > > > t1
>
> > > > id id1 id2
> > > > 1 0 -1
> > > > 2 0 -3
> > > > 3 8 -4
> > > > 4 0 -5
>
> > > > I want to:
> > > > update t1 set id1=min(id2) where id1=0.
> > > > but each id1 should get updated with one value greater than the
> > > > previous value.
>
> > > > Means, here the min(id2) is -5, so all id1=0 record should get updated
> > > > starting with -6, -7, -8 and so on.
>
> > > > Output like
>
> > > > id id1 id2
> > > > 1 -6 -1
> > > > 2 -7 -3
> > > > 3 8 -4
> > > > 4 -8 -5
>
> > > > Can anyone help me build this logic?
>
> > > > Help would be appreciated
>
> > > > TIA
>
> > > CREATE TABLE t1 (
> > > id NUMBER(2),
> > > id1 NUMBER(2),
> > > id2 NUMBER(2));
>
> > > INSERT INTO t1
> > > SELECT 1, 0, -1 FROM dual union
> > > SELECT 2, 0, -3 FROM dual union
> > > SELECT 3, 8, -4 FROM dual union
> > > SELECT 4, 0, -5 FROM dual ;
>
> > > UPDATE t1 SET
> > > id1=
> > > -ROWNUM+(SELECT Min(id2) FROM t1 WHERE id1=0)
> > > WHERE id1=0;
>
> > > This gives the expected output of your particular example.
>
> > > BTW "one value greater" than -5 is -4, not -6 :)- Hide quoted text -
>
> > > - Show quoted text -
>
> > Thanks David, Chris. That was helpful.
>
> > One more point, what if I want to update id based on some group by
> > condition.
> > Suppose the structure changes to
>
> > t1
>
> > id id1 id2 sign
> > 1 0 -1 A
> > 2 0 -3 A
> > 3 8 -4 B
> > 4 0 -5 B
> > 5 0 -5 B
>
> > and I would like to apply the same logic grouping on sign.
> > Output like
>
> > id id1 id2 sign
> > 1 -6 -1 A
> > 2 -7 -3 A
> > 3 8 -4 B
> > 4 -6 -5 B
> > 5 -7 -5 B
>
> > Something like
>
> > UPDATE t1
> > SET id1=-ROWNUM+(SELECT Min(id2) FROM t1 WHERE id1=0)
> > WHERE id1=0
> > GROUP BY sign;
>
> > Any idea?
>
> > TIA
>
> Sorry I don't know enough SQL to do it in one single statement.
> Here's some PL/SQL code to do it. Basically repeats the update
> statement for every value of "sign".
>
> CREATE TABLE t1 (
> id NUMBER(2),
> id1 NUMBER(2),
> id2 NUMBER(2),
> ssign CHAR(1));
>
> INSERT INTO t1
> SELECT 1, 0, -1,'A' FROM dual union
> SELECT 2, 0, -3,'A' FROM dual union
> SELECT 3, 8, -4,'B' FROM dual union
> SELECT 4, 0, -5,'B' FROM dual union
> SELECT 5, 0, -5,'B' FROM dual ;
>
> BEGIN
> DECLARE
> CURSOR cur_signs is
> SELECT DISTINCT ssign FROM t1;
> min_value NUMBER;
>
> BEGIN
>
> SELECT Min(id2) INTO min_value FROM t1
> WHERE id1=0;
>
> FOR rrow IN cur_signs LOOP
> UPDATE t1 SET
> id1= min_value - ROWNUM
> WHERE id1=0 AND ssign=rrow.ssign;
> END LOOP;
>
> END;
> END;
> /- Hide quoted text -
>
> - Show quoted text -

Thanks Chris.
Even I didnt came up with any idea to do it in single sql and went for pl/sql.
The reason I asked for single sql was, we have records in millions (around 30 million) and
achieving the update in pl/sql might affect the performance (correct me if i am wrong)
Can you or anyone tell me some points to keep in mind when implementing the logic in pl/sql?
(I have already looked into bulk collect feature). Is doing this in single sql better than using pl/sql?

TIA Received on Mon Jun 25 2007 - 10:08:33 CDT

Original text of this message

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