Question

Draw the entities and relationships suggested by each word problem.  Include the proper foreign key(s).  Remember to make a copy for yourself.  

A course may have many sections or not be offered at all (no sections).  Sections always belong to a single course.  Students take at least one and often multiple sections during a semester.  We want to capture a student’s grade and, if that grade is an F, last date attended.  Courses have a CID, course name and department.  Sections have a CRN, a room and a time.  Sections have no students, or many students.  Students have a CWID, name and year (like Sophomore).

Answer 1

ANS. In this question, according to provided information, we have 4 entities with attributes (in parenthesis) as:

1. Course(CID,course name,department) may have one or more sections
2. Student(CWID,name,year,CID) may take one or multiple sections in a semester
3. Section(CRN,room,time)
4. Result(Fail, Pass)

Here, the student may opt for any course in a department so, CID will be foreign key as it is a primary key in the Course table and column of the Student table as Student may opt course of particular CID.

The following diagram shows the Entity-Relationship Model for this Student-Course data model.

course name De ( CID department course COURSE (CRN name selects room CWID CWID STUDENT STUDENT opt for promoted SECTION semester SUCCESS time year scores yields GRADE < calculate RESULT FAILURE last date attended

In the above diagram, CID, CWID, CRN are underlined and are unique keys and primary keys to respective tables.

Here, symbol M represents a one-to-many relationship as one course may have more than one section.

The Result is a weak entity and represented by a double rectangle as it is dependent on Grades.