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create table customers(id int primary key,name varchar(10),age int,address varchar(15),salary decimal(10,2)); drop trigger if exists salary_difference_trigger create or replace trigger salary_difference_trigger before insert or update or delete on customers for each row declare old_salary number; new_salary number; begin if inserting or updating then old_salary := NVL(:old.salary,0); new_salary :=NVL(:new.salary,0); dbms_output.put_line('Salary difference:'||(new_salary-old_salary)); elseif deleting then old_salary :=NVL(:old.salary,0); dbms_output.put_line('salary before deletion:'||old_salary); end if; end; /