1. Create employee table with following attributes (empid NUMBER, empname VARCHAR(10), dept VARCHAR(10),salary NUMBER);
2. Create salary_log table with following attributes (log_id NUMBER GENERATED ALWAYS AS IDENTITY, empid NUMBER,empname VARCHAR(10),old_salary NUMBER,new_salary NUMBER,update_date DATE);
3. Create a trigger named as log_salary-update.
4. Inside the trigger block, Insert the values into the salary_log table whenever the salary is updated.
5. End the trigger.
6. Update the salary of an employee in employee table.
7. Whenever a salary is updated for the employee it must be logged into the salary_log table with old salary and new salary.
8. Display the employee table, salary_log table.

CREATE TABLE employee(empid NUMBER, empname VARCHAR(10), dept VARCHAR(10),salary NUMBER);

CREATE TABLE salary_log(log_id NUMBER , empid NUMBER,empname VARCHAR(10),
                        old_salary NUMBER,new_salary NUMBER,update_date DATE);

CREATE OR REPLACE TRIGGER log_salary_update
BEFORE UPDATE ON employee
FOR EACH ROW
DECLARE
    v_old_salary NUMBER;
    v_new_salary NUMBER;
BEGIN
    v_old_salary := :old.salary;
    v_new_salary := :new.salary;

    IF v_old_salary <> v_new_salary THEN
        INSERT INTO salary_log (empid, empname, old_salary, new_salary, update_date)
        VALUES (:old.empid, :old.empname, v_old_salary, v_new_salary, SYSDATE);
    END IF;
END;
/

Thus the trigger using pl/sql has been created sucessfully.