Consider the relation schema of the COMPANY database given below
EMPLOYEE (fname, minit, lname, ssn, birthdate, address, sex, salary, superssn, dno)
KEY: ssn
DEPARTMENT (dname, dnumber, mgrssn, mgrstartdate)
KEY: dnumber.
PROJECT (pname, pnumber, plocation, dnum)
KEY: pnumber.
WORKS_ON (essn, pno, hours)
KEY: (essn, pno)
DEPENDENT (essn, dependent-name, sex, bdate, relationship)
KEY: (essn, dependent-name)
Write a PL/SQL TRIGGER(s) to enforce the following business rules
An employee can not have a salary higher than that of his/her direct supervisor;
The company's 'Line of Command' is enforced in strict hierarchical order. Each employee must have a direct supervisor.
No employee is allowed to be supervised by him or herself. The ONLY exception to this rule applies to Mr. Borg (888665555) who is the company's president (he is supervised by NULL).