Question

Suppose we have a trigger, named Foo.

Foo depends on the T table and depends on the a, b, c columns.

If the T table is dropped, the T trigger is also dropped?

If c is deleted, is the T trigger dropped?

If an alteration happens for the T table, but it doesn’t affect the a, b, c columns, is the T trigger dropped?

Thank you in advance for your answers,

Best regards,
Lajos Arpad.

Answer 1

The only scenario where a trigger is dropped without an explicit

DROP TRIGGER <trigger_name>;

Is when the table is also dropped.

DROP <TABLE_NAME>;  

In cases where the source code of the trigger references schema that is no longer present, the trigger becomes invalid. You can query your database for invalid objects with:

   select * from user_objects where status != 'VALID'  
   -- invalid objects associated with the user you are logged in as
   select * from all_objects where status != 'VALID' 
   -- all invalid objects  in the database

There is a case where a drop ‘cascades’ when you specify a cascade. But this is focused on dropping child tables.

drop table <table_name> cascade constraints;

Oracle 10g documentation on DROP TABLE DDL command.

All that said triggers are often misused and introduce bugs. I would encourage you to avoid placing your application logic in them.