Answer Happy

Section B 4. (a) Explain how to respectively enforce the entity integrity and the referential integrity. (4 marks) (b) Explain how to decide whether a relationship is a strong relationship or a weak relationship in Entity-Relationship model. In the Entity-Relationship diagram, explain how to represent strong relationships. (3 marks) (c) Referring to the following descriptions, draw ER diagrams of the entities “Club”, “Project”, “Staff”, “Student" and their relationships (marking the cardinality) using Crow's Foot Model. You do NOT need to write the attributes of each entity. • There are several clubs, and each club is managed by a staff. Each staff can manage at most one club. Some staff does not manage any club. • Students and staff can join the clubs as a member. Each student or staff can be the member of at most one club. Some students or staff may not be the member of any club. Each club has at least one student member and at least one staff member. • There are several projects running at the same time. Each project is coordinated by one staff, and one staff can coordinate at most one project. • Each student may participate in several projects. A student may or may not participate in the projects, and one student can participate in several projects at the same time. Each project has at least one student. (9 marks) (d) Suppose a teacher can teach several courses, and one course can be taught by several teachers. Transfer the many-to-many relationship in Table Q4 into the form that can be directly implemented in a relational database. (4 marks)