Fundamentals of Database Systems 4th Edition chapter 07精品.pdfVIP

Chapter 7 Relational Database Design by ER- and EERR-to-Relational Mapping Copyright © 2004 Pearson Education, Inc. Chapter Outline ER-to-Relational Mapping Algorithm Step 1: Mapping of Regular Entity Types Step 2: Mapping of Weak Entity Types Step 3: Mapping of Binary 1:1 Relation Types Step 4: Mapping of Binary 1:N Relationship Types. Step 5: Mapping of Binary M:N Relationship Types. Step 6: Mapping of Multivalued attributes. Step 7: Mapping of N-ary Relationship Types. Mapping EER Model Constructs to Relations Step 8: Options for Mapping Specialization or Generalization. Step 9: Mapping of Union Types (Categories). Elmasri/Navathe, Fundamentals of Database Systems, Fourth Edition Chapter 7-3 Copyright © 2004 Ramez Elmasri and Shamkant Navathe ER-to-Relational Mapping Algorithm Step 1: Mapping of Regular Entity Types. – For each regular (strong) entity type E in the ER schema, create a relation R that includes all the simple attributes of E. – Choose one of the key attributes of E as the primary key for R. If the chosen key of E is composite, the set of simple attributes that form it will together form the primary key of R. Example: We create the relations EMPLOYEE, DEPARTMENT, and PROJECT in the relational schema corresponding to the regular entities in the ER diagram. SSN, DNUMBER, and PNUMBER are the primary keys for the relations EMPLOYEE, DEPARTMENT, and PROJECT as shown. Elmasri/Navathe, Fundamentals of Database Systems, Fourth Edition Chapter 7-4 Copyright © 2004 Ramez Elmasri and Shamkant Navathe FIGURE 7.1 The ER conceptual schema