Consider the following relational schema: Department(deptid, dname, location) Student(snum, sname, deptid, age) Faculty (fid, fname, deptid) Class(cname, deptid meets_at, room, faculty) Enrolled(snum. cname, score, grade) Assume that: All students and faculty members must major/work in one depart- ment; Faculty teach courses only in the department they belong to; The names of the courses are unique for each department Scores are numbers in [0,100]; Faculty in Table Class is a subset of fid in Table Faculty Write each of the following queries using Datalog. If you believe any one of the following is not expressible in Datalog, informally explain why it can- not be expressed 7. (10 pts) Find the faculty who have instructed at least one course in the CS department but have never instructed any course in the Math- ematics department. 8. (10 pts) Find the names of courses each student gets the lowest score in, i.e., if a student takes 2 courses A and B and scores 50 and 60, respectively, then A is the name of the course in which that stu- dent (can be different for different students depending on their score) has scored the lowest 9. (15 pts) What are the possible outcomes if a Datalog rule is unsafe? Please illustrate two different scenarios for this case by designing un- safe rules for the relational schema mentioned above, and explain the answers to these rules Consider the following relational schema: Department(deptid, dname, location) Student(snum, sname, deptid, age) Faculty (fid, fname, deptid) Class(cname, deptid meets_at, room, faculty) Enrolled(snum. cname, score, grade) Assume that: All students and faculty members must major/work in one depart- ment; Faculty teach courses only in the department they belong to; The names of the courses are unique for each department Scores are numbers in [0,100]; Faculty in Table Class is a subset of fid in Table Faculty Write each of the following queries using Datalog. If you believe any one of the following is not expressible in Datalog, informally explain why it can- not be expressed 7. (10 pts) Find the faculty who have instructed at least one course in the CS department but have never instructed any course in the Math- ematics department. 8. (10 pts) Find the names of courses each student gets the lowest score in, i.e., if a student takes 2 courses A and B and scores 50 and 60, respectively, then A is the name of the course in which that stu- dent (can be different for different students depending on their score) has scored the lowest 9. (15 pts) What are the possible outcomes if a Datalog rule is unsafe? Please illustrate two different scenarios for this case by designing un- safe rules for the relational schema mentioned above, and explain the answers to these rules
