Write the following queries in relational algebra, using the university schema.
a. Find the titles of courses in the Comp. Sci. department that have 3 credits.
∏title(σdept='Comp.Sci'∧credits=3(course))
b. Find the IDs of all students who were taught by an instructor named Einstein;
make sure there are no duplicatesin the result.
c. Find the highest salary of any instructor.
Gmax(salary)(instructor)
d. Find all instructors earning the highest salary (there may be more than one with the same salary).
instructor ⋈ (Gmax(salary) as salary(instructor))
Note that the above query renames the maximum salary as salary,
so the subsequent natural join outputs only instructors with that salary
e. Find the enrollment of each section that was offered in Autumn 2009.
course_id,section_id Gcount(∗) as enrollment(σyear=2009∧semester=Autumn(takes))
f. Find the maximum enrollment, across all sections, in Autumn 2009.
t1 ← course id,section idGcount(∗) as enrollment(syear=2009∧semester=Autumn(takes)) result = Gmax(enrollment)(t1)
g. Find the sections that had the maximum enrollment in Autumn 2009.
t2 ← Gmax(enrollment) as enrollment(t1) where t1 is as defined in the previous part of the question. result = t1 ⋈ t2