What are the names and salaries for instructors who earn less than the average salary of instructors in the Physics department?
SELECT name ,  salary FROM instructor WHERE salary  <  (SELECT avg(salary) FROM instructor WHERE dept_name  =  'Physics')
names and salaries for instructors = SELECT name, salary FROM instructor; earn less than the average salary = salary < (SELECT AVG(salary)); in the Physics department = WHERE dept_name = 'Physics';