using postgresql: Write a trigger that will be activated when a new customer is added to the Customers table and that verifies that the ID of the new record does not yet exist in the table. If it...

using postgresql:

Write a trigger that will be activated when a new customer is added to the Customers table and that verifies that the ID of the new record does not yet exist in the table. If it does, the request shall be rejected.

Show what happens when a record with an existing ID is attempted to be added to the Customer table to verify that your trigger is working properly.

Customers table columns: id, first name, last name, email