need help with this two quieries. students(sid,name,age,gpa) // sid is the prima

Question

need help with this two quieries.

students(sid,name,age,gpa) // sid is the primary key

courses(cid,deptid, description) // cid,deptid is the primary key

professors(ssn,name,address,phone,deptid) // ssn is the primary key

enrollment(sid,cid,section,grade) cid makes reference to the courses table. // sid, cid, and section is the primary key

teaches(cid,section,ssn). cid, section makes reference to the enrollment table // cid, section is the primary key

a. Find the name of the professor with the maximum percentage of students that failed his course.

b. On average what percentage of students fail a course? (total number of students that failed a course / total number of enrolled students).

Explanation / Answer

a.)

select p.name
from professors p
left outer join teaches t
on p.ssn=t.ssn
left outer join enrollment e
on t.cid = e.cid
left outer join students s
on e.sid = s.sid
where e.grade='F'

GROUP BY p.name
ORDER BY count(s.sid)

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