IS NULL OPERATOR Let’s list the employees that have manager. SELECT first_name,last_name, manager_id FROM hr.employees WHERE manager_id IS not NULL;   LOGICAL OPERATORS AND : It returns TRUE if all operands are TRUE.   OR : It returns TRUE if any operand is TRUE.   NOT : It returns the reverse of the result.   … Continue reading Oracle SQL Tutorials – Chapter 2 (Part 2 of 3)