Automatically update foreign key

Question

Hello,
I am new into Application Express and currently developing an application to handle amongst other things databases with instances and users. The databases have an internal 10-digit number (ID) as primary key. This number can be found in the instances and user table as a foreign key. However, it is possible that the databases unique 10-digit ID changes and I wan't to know if it's possible to automatically update the foreign key in the instances and in the user table when the database ID is changed or if it is possible at all to change a primary key?
I have created a report of existing databases with a link on the name of each database directing to another page where you can change every value for the selected database. This works properly and I wan't to enable for the database ID to be changed here as well (and to automatically update all tables where the ID is a foreign key) if it's possible.
Thank you in advance
Fabian

Answer 1

Hi Fabian,
you can also use a trigger to do the Foreign key update on your child tables.
In my example the trigger will only fire if the primary key (JOB_ID) of the JOBS table gets updated. In that case it will update all records in the detail table EMPLOYEES to the new primary key value.
CREATE OR REPLACE TRIGGER TRG_JOBS_PK_UPDATE
AFTER UPDATE
OF JOB_ID
ON JOBS
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
BEGIN
    UPDATE EMPLOYEES
       SET JOB_ID = :NEW.JOB_ID
     WHERE JOB_ID = :OLD.JOB_ID
END;Hope that helps
Patrick
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