thanks
i found my mistake :

there are deleted rows , so
row_id has wrong values

Maurizio

Maurizio ha scritto:

>
> i tryed
>
> UPDATE myTable m
> SET m.field_b =
> (
> SELECT m2.field_a
> from myTable m2
> where m2.row_id = m.row_id + 1
> ) where m.row_id is not null
>
> it writes null values ,
> but if i try
>
> UPDATE myTable m
> SET m.field_b =
> (
> SELECT m2.field_a
> from myTable m2
> where m2.row_id = m.row_id
> ) where m.row_id is not null
>
> it works .
>
> row_id is integer pk
> field_a and field_b are char 80
>
> thanks
>
> Fidel Viegas ha scritto:
> >
> > On Fri, Jun 13, 2008 at 12:03 PM, Svein Erling Tysvær
> > <svein.erling.tysvaer@...
> <mailto:svein.erling.tysvaer%40kreftregisteret.no>
> > <mailto:svein.erling.tysvaer%40kreftregisteret.no>> wrote:
> > > What you do should work. The one thing I would expect to cause this
> > to fail,
> > > is if you didn't commit the transaction. Another things that could
> be of
> > > influence, is the field type of row_id, if it is an integer, decimal
> > or date
> > > (provided dialect 3) field, I cannot see how this could fail.
> > Floating point
> > > numbers is something completely different, they're approximate (may be
> > > 1.00000000232 when you think it is just 1) and shouldn't be used with
> > > comparison for equality. Of course, if field_a and field_b is
> > incompatible
> > > field types, then you would also get trouble, but that would
> normally be
> > > very visible for you when you try to prepare the statement.
> >
> > Hi Set,
> >
> > >From what I can see in the statement, that will update every single
> > row, because there is no filter condition in the update statement
> > itself.
> >
> > if you do "update table set col = xxx", this will change every single
> > row in the table. The subselect is correct, but that is a condition
> > missing in the udpate statement, which I haven't figured out what it
> > is. Here is how it should be:
> >
> > UPDATE myTable m
> > SET m.field_b =
> > (
> > SELECT m2.field_a
> > from myTable m2
> > where m2.row_id = m.row_id + 1
> > ) where <condition>;
> >
> > I haven't really figured what the <condition> is, but would like to
> > know if someone comes up with the solution to this.
> >
> > Fidel.
> >
> >
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> 12/06/2008 16.58
> >
>
>
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