Find the name and salary of instructors whose salary is below the average salary of the instructors in the Physics department.
SELECT name ,  salary FROM instructor WHERE salary  <  (SELECT avg(salary) FROM instructor WHERE dept_name  =  'Physics')
salary below the average salary of instructors in a specific department refers to salary < (SELECT AVG(salary) FROM department_specific_table); instructors in the Physics department refers to dept_name = 'Physics';