I'm working with IBO 4.3Aa and today I have discovered strange
behaviour. I have a TIB_Query PCQuery, that selects the products with
the select-statement:
select PCID,
PCMPID,
(select MPNAME from MAINPRODUCTGROUPS where
MPID=PRODUCTS.PCMPID) as MPNAME,
PCNAME from PRODUCTS

PCMPID is a foreign key, that points to the table MAINPRODUCTGROUPS.
There is another TIB_Query MPQuery, that selects the Main-Productgroups
with the select-statement:
select MPID,
MPNAME
from MAINPRODUCTGROUPS

The KeySource of MPQuery is assigned to the DataSource of PCQuery and
the KeyLinks-Property of MPQuery is MAINPRODUCTGROUPS.MPID=PRODUCTS.PCMPID

In the OnDataChange-Event of PCQuery I have the following code-snippet:
if Assigned(Field) and (CompareText('PCMPID',Field.FieldName)=0) then
ShowMessage('Main-Productgroup has changed');

Now I run my test-app and change the value of MPQuery via a
TIB_LookupCombo and the MessageBox pops up. That's the expected behaviour.

Now I set the KeyDescLinks-Property of MPQuery to MPNAME=MPNAME
and run the test-app again. When I change the value of MPQuery nothing
happends and when I debug the test-app, I can see, that the
OnDataChange-Events fires, but the field-parameter is always null.

Am I doing something wrong or does IBO something wrong :-)

Any help is appreciated.

Regards

Guido