tailieunhanh - Database Design Using Entity-Relationship Diagrams phần 5

Xe có thể được điều khiển bởi nhiều học sinh d. Mỗi chiếc xe phải được thúc đẩy bởi nhiều sinh viên. Các quy tắc cardinality trên là tùy chọn? Trong đó quy định là bắt buộc? Diagramatically hiển thị các mối quan hệ. | c. Each car can be driven by many students d. Each car must be driven by many students. Which of these above cardinality rules are optional Which rules are mandatory Diagramatically show these relationships. References Batani C. Ceri S. and Navathe . Conceptual Database Design. Benjamin Cummings Publishing Redwood City CA 1992. Earp R. and Bagui S. Extending Relationships in the Entity Relationship Diagram Data Base Management Auerbach Publications Boca Raton FL 22-10-42 1-14 May 2001. Elmasri R. and Navathe . Fundamentals of Database Systems 3rd ed. Addison-Wesley Reading MA 2000. Kroenke . Database Processing Prentice Hall Upper Saddle River NJ 2000. McFadden . and Hoffer . Modern Database Management 4th ed. Benjamin Cummings Publishing Redwood City CA. 1994. Ramakrishnan R. and Gehrke J. Database Management Systems 3rd ed. McGraw-Hill New York 2003. Sanders L. Data Modeling Boyd Fraser Publishing Danvers MA 1995. Case Study West Florida Mall continued In the past few chapters we selected our primary entities as per the specifications from the user so far and defined the relationships between the primary entities. In this chapter we proceed with the ER diagram for this case study by looking at steps 6 and 7 of the ER design methodology and map the ER diagram to a relational database with some sample data as we proceed. Step 6 develops the structural constraints of binary relationship by stating Step 6 State the exact nature of the relationships in structured English from all sides. For Example if a relationship is A B 1 M then there is a relationship from A 1 to B M and from B M back to A 1 . Refer to Figure . Figure An ER Diagram of West Florida Mall with Four Entities and Structural Constraints First for the relationship located_in From MALL to STORE this fits Pattern 3 1 full N One mall must have many at least one stores. or Malls which are recorded in the database must have many one or more stores located in them. From STORE to MALL .