Assignment 2 - Chapter 4 Case: Q12. TEC’s management wants to keep track of the following entities: COMPANY, OPENING, QUALIFICATION, CANDIDATE, JOB_HISTORY, PLACEMENT, COURSE, and SESSION. Given that information, do the following: 1. 2. 3. 4. 5. Draw the Crow’s Foot ERDs for this enterprise. Identify all necessary relationships. Identify the connectivity for each relationship. Identify the mandatory and optional dependencies for the relationships. Resolve all M:N relationships. Sol: Crow’s Foot ERD, relationships, connectivity & dependencies & resolution of M:N relationships: - Each COMPANY may list many OPENING. OPENING is dependent on COMPANY as it must be listed by the COMPANY. When there is an OPENING, there can be a PLACEMENT. Therefore, considering it is a weak relationship. A CANDIDATE may be placed in the PLACEMENT of an OPENING. OPENING and CANDIDATE have a M:N relationship as one candidate can fill many openings. This is decomposed to two 1:M relationships using the PLACEMENT as the composite entity becoming the bridge between the two. CANDIDATE may have many jobs creating JOBHISTORY. But this is optional to CANDIDATE. Also, PLACEMMENT is optional to JOBHISTORY as only TEC’s record is noted. CANDIDATE can earn one or more QUALIFICATION. It is optional to have a specific QUALIFICATION. Each QUALIFICATION may be earned by many CANDIDATES. Therefore it is a M:N relationship. This is decomposed using the EDUCATION entity. - Each OPENING requires a QUALIFICATION. QUALIFICATION may have many openings, but Qualification does not require an OPENING. Therefore, OPEINING is optional to QUALIFICATION. Similarly, COURSE may have many SESSIONS, but a SESSION can have only one COURSE. But every course does not need a session making it a weak relationship. CANDIDATE must ENROLL in a SESSION. Each SESSION Must have at least one CANDIDATE. CANDIDATE can ENROLL in many SESSIONS Each ENROLL can have many CANDIDATE. CANDIDATE & SESSION is a M:N relationship which is decomposed using ENROLL as the composite entity. Each SESSION has a COURSE. But a COURSE does not need to have a SESSION. Therefore they have a weak relationship.
