Обсуждение: Interest IN problem on 7.4

Hi,

I am using pg 7.4.

Pls, see this test:

tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
dog_or_free=4 and ids NOT IN ( select oc.ids_car_real from a_oferti_cars
oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964)   AND
IDS = 'SOF_9989';
UPDATE 0
tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
dog_or_free=4 and ids IN ( select oc.ids_car_real from a_oferti
_cars oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964)
AND IDS = 'SOF_9989';
UPDATE 0
tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
dog_or_free=4 and ids NOT IN ( select oc.ids_car_real from a_oferti_cars
oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964 AND
OC.IDS_CAR_REAL IS NOT NULL)   AND IDS = 'SOF_9989';
UPDATE 1

I think IN is not working correct in this case.

In my case A_CARS.IDS is name and also OC.IDS_CAR_REAL.

It is interest that the last update is working well and the first one
not.

Pls, comment this problem.

regards,
ivan.

On Sat, 13 Dec 2003, pginfo wrote:

> Hi,
>
> I am using pg 7.4.
>
> Pls, see this test:
>
> tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
> dog_or_free=4 and ids NOT IN ( select oc.ids_car_real from a_oferti_cars
> oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964)   AND
> IDS = 'SOF_9989';
> UPDATE 0
> tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
> dog_or_free=4 and ids IN ( select oc.ids_car_real from a_oferti
> _cars oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964)
> AND IDS = 'SOF_9989';
> UPDATE 0
> tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
> dog_or_free=4 and ids NOT IN ( select oc.ids_car_real from a_oferti_cars
> oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964 AND
> OC.IDS_CAR_REAL IS NOT NULL)   AND IDS = 'SOF_9989';
> UPDATE 1
>
> I think IN is not working correct in this case.

A NOT IN (subselect) when the subselect contains a NULL cannot ever return
true by specification.

--------------
A NOT IN (subselect) -> NOT (A IN (subselect))
NOT (A IN (subselect)) -> NOT (A = ANY (subselect))

The result of A = ANY (subselect) is derived by the application of the
implied comparison predicate, R = RT for every row RT in the subselect.

If the implied comparison predicate is true for at least one row RT then A
= ANY (subselect) is true.  If the subselect is empty or the implied
predicate is false for every row RT then A = ANY (subselect) is false.
Otherwise it is unknown.

For the one element row RT, A = RT where RT is a NULL returns unknown.
Therefore, we know that it's not an empty subselect (it returns at least
one row containing NULL -- that's our precondition), and that it does not
return false for every row, so A = ANY (subselect) is either true or
unknown depending on whether there's another row which does match, so
NOT(A = ANY(subselect)) is either false or unknown.

Hi,
thanks a lot.
All is ok now.

regards,
ivan.

Stephan Szabo wrote:

> On Sat, 13 Dec 2003, pginfo wrote:
>
> > Hi,
> >
> > I am using pg 7.4.
> >
> > Pls, see this test:
> >
> > tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
> > dog_or_free=4 and ids NOT IN ( select oc.ids_car_real from a_oferti_cars
> > oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964)   AND
> > IDS = 'SOF_9989';
> > UPDATE 0
> > tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
> > dog_or_free=4 and ids IN ( select oc.ids_car_real from a_oferti
> > _cars oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964)
> > AND IDS = 'SOF_9989';
> > UPDATE 0
> > tt07=# update a_cars set dog_or_free=0 where virtualen=0 and
> > dog_or_free=4 and ids NOT IN ( select oc.ids_car_real from a_oferti_cars
> > oc,a_oferti o where oc.IDS_oferti=o.ids  and o.date_valid>=9964 AND
> > OC.IDS_CAR_REAL IS NOT NULL)   AND IDS = 'SOF_9989';
> > UPDATE 1
> >
> > I think IN is not working correct in this case.
>
> A NOT IN (subselect) when the subselect contains a NULL cannot ever return
> true by specification.
>
> --------------
> A NOT IN (subselect) -> NOT (A IN (subselect))
> NOT (A IN (subselect)) -> NOT (A = ANY (subselect))
>
> The result of A = ANY (subselect) is derived by the application of the
> implied comparison predicate, R = RT for every row RT in the subselect.
>
> If the implied comparison predicate is true for at least one row RT then A
> = ANY (subselect) is true.  If the subselect is empty or the implied
> predicate is false for every row RT then A = ANY (subselect) is false.
> Otherwise it is unknown.
>
> For the one element row RT, A = RT where RT is a NULL returns unknown.
> Therefore, we know that it's not an empty subselect (it returns at least
> one row containing NULL -- that's our precondition), and that it does not
> return false for every row, so A = ANY (subselect) is either true or
> unknown depending on whether there's another row which does match, so
> NOT(A = ANY(subselect)) is either false or unknown.