Checking Referential Integrity prior to Delete in APEX 20.1

Question

When a user tries to delete a code/validation record, I would like to check to see if the code in that record has been used prior to the deletion attempt so I can display a message that is more meaningful than an Oracle constraint error.

For example: "This code cannot be deleted because it has been referenced in a course record. Please inactivate it instead."

Can anyone give me general advice on the approach to take?

My first thought was to create a dynamic action associated with the Delete button. I think there is probably a better way, however.

Answer 1

You've said it - create a validation , they are designed for such a purpose. Make it a Function body returning error text . Write your piece of code and display a message. Something like

declare
  l_var number;
begin
  select d.blabla
    into l_var
    from detail_table d
    where ...;

  if l_var is not null then
     return ('This code can not be deleted etc.');
  end if;
end;

Answer 2

I prefer the notion of catching errors if they happen using the application error handler https://docs.oracle.com/en/database/oracle/application-express/20.2/htmdb/editing-application-attributes.html#GUID-B744BE26-69B6-4084-A217-114CF05A5A4B

The sample provides detail on how to translate any known constraints to a more user-friendly message.

The danger with creating a DA along the lines of your suggestion is there may be a time difference, however small, between the check & display, and the actual delete attempt.