$7.$ Write the following queries in SQL$,$ using the university schema, execute your SQL statement

on the sample database with small relations and show me both the SQL statements and the query

results $(20$ points, $4$ points each$)$

a$.$ Find the names of all students who have taken at least two courses offered by Comp.

Sci. department; make sure there are no duplicate names in the result. Note that

student in other departments can take courses from Comp. Sci. as well.

b$.$ Find the IDs and names of all students who have not taken any course offering in $2017.$

c$.$ For each department, find the name and salary of the instructor who earns the minimum

salary in that department. You may assume that every department has at least one

instructor.

d$.$ Find the highest, across all departments, of the per$-$department minimum salary

computed by the preceding query $($part $7.$c$).$

e$.$ Find the course titles of all prerequisite courses of $$CS$-319.$