Question

Consider the following relations:

Student(sID, surName, firstName, campus, email)

Course(dept, cNum, name)


Offering(oID, dept, cNum, term, instructor)


Took(sID, oID, grade)

Such as:

Offering[dept, cNum] ⊆ Course[dept, cNum]

Took[sID] ⊆ Student[sID]


Took[oID] ⊆ Offering[oID]

1. Find the Terms when the course number “369” by the department “CS” was not offered.

Answer 1

answer)

π_{Offering.term}(σ _{Offering.cNum=Course.cNum and Course.cNum!=369 and Course.dept="CS"} ( Course x Offering )) this is used to find the terms wher course number “369” by the department “CS” was found.so we need to remove all the terms which occur when course number “369” by the department “CS” from total terms inorder to get the course number “369” by the department “CS” was not offered.

π_{Offering.term} (Offering)-π_{Offering.term}(σ _{Offering.cNum=Course.cNum and Course.cNum!=369 and Course.dept="CS"} ( Course x Offering ))