Fundamentals of Database Management Systems, Second Edition

CHAPTER 5

THE RELATIONAL DATABASE MODEL: INTRODUCTION

In 1970, Dr. Edgar F. (Ted) Codd of IBM published in Communications of the ACM a paper entitled “A Relational Model of Data for Large Shared Data Banks.” This paper marked the beginning of the field of relational databases. During the 1970s, the relational approach to databases progressed from being a technical curiosity to a subject of serious interest in the information systems community. But it was not until the early 1980s that commercially viable relational database management systems became available. There were two basic reasons for this. One was that, while the relational database was very tempting in concept, its application in a real-world environment was elusive for performance-related reasons. The second reason was that at exactly the time that Codd's paper was published, the earlier hierarchical and network database management systems were just coming onto the commercial scene and were the focus of intense marketing efforts by the software and hardware vendors of the day. Eventually, both of these obstacles were overcome and the relational model became and remains the database model of choice.

OBJECTIVES

• Explain why the relational database model became practical in about 1980.
• Define such basic relational database terms as relation and tuple.
• Describe the major types of keys including primary, candidate, and foreign.
• Describe how one-to-one, one-to-many, and many-to-many binary relationships are implemented in ...