Write the following queries in SQL, using the university schema. (You should actually check the queries you write on the database.)
(a) to find the names of all instructors whose salary is more than the 90% of the department average salary.
(b) for each course section offered in 2009, find the average total credits (tot cred) of all students enrolled in the section, if the section had at least 2 students
(c) to insert into instructors those students who have earned more than 140 credits with salary 90000 to their respective departments.
(d) to raise salary of instructors by 10% unless the salary becomes greater than 90,000; in such cases, give only a 3% raise.
(e) to delete all instructors whose salary is less than half of the average salary of all instructors.