TOWSON AIT 632 - ER-Exercise 1 (17 pages)

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ER-Exercise 1



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ER-Exercise 1

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Pages:
17
School:
Towson University
Course:
Ait 632 - Database Management Systems

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ER Exercise 1 Sungchul Hong A School Database A college is divided into several schools Each school is administered by a dean A dean is a professor Each school is composed of several departments For example the school of business has an accounting department a management marketing economics finance and CIS department 1 1 IS DEAN OF PROFESSOR 1 1 School has minimum of deans School has maximum of deans A professor could be a dean of minimum of schools A professor could be a dean of maximum of schools 0 1 SCHOOL 1 1 1 OPERATES 1 DEPARTMENT M Each department offers several courses It can have M 1 OFFERS COURSE DEPARTMENT 1 1 1 A course can have many sections 1 HAS M SECTIONS COURSE 1 1 0 Sections can have minimum one and maximum one course Each department has many professors assigned to it One of those professors chairs the department Only one of the professors can chair the department to s he is assigned and no professor is required to accept the chair position Therefore DEPARTMENT is optional to PROFESSOR in the chairs relationship 1 PROFESSOR 1 1 M Chairs 1 0 1 DEPARTMENT 1 1 1 1 IS ASSIGNED TO Each professor may teach up to four classes each one a section of a course A professor may also be on a research contract and teach no classes at all M 1 teaches PROFESSOR 1 1 CLASS 0 4 A student may enroll in several classes but s he takes each class only once during any given enrollment period Each class may have up to 30 students in it ENROLL STUDENTS 8 30 How can we enforce the rule that restrict taking same section multiple times in same semester SECTION 1 8 How can we represent grade Each department has several students whose major is offered by that department However each student has only a single major and is therefore associated with a single department 1 M enrolls DEPARTMENT 1 1 STUDENT 1 Each student has an advisor in his or her department each advisor counsels several students An advisor is also a professor but not all professors advise students 1 M advise



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