Fundamentals of Database Systems (7th Edition)
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For database systems courses in Computer Science
This book introduces the fundamental concepts necessary for designing, using, and implementing database systems and database applications. Our presentation stresses the fundamentals of database modeling and design, the languages and models provided by the database management systems, and database system implementation techniques.
The book is meant to be used as a textbook for a one- or two-semester course in database systems at the junior, senior, or graduate level, and as a reference book. The goal is to provide an in-depth and up-to-date presentation of the most important aspects of database systems and applications, and related technologies. It is assumed that readers are familiar with elementary programming and data-structuring concepts and that they have had some exposure to the basics of computer organization.
index. We then showed how multilevel indexes can be implemented as B-trees and B+-trees, which are dynamic structures that allow an index to expand and shrink dynamically. The nodes (blocks) of these index structures are kept between half full and completely full by the insertion and deletion algorithms. Nodes eventually stabilize at an average occupancy of 69 percent full, allowing space for insertions without requiring reorganization of the index for the majority of insertions. B+-trees can
general, specify a query such as "retrieve the supervisees of ‘James Borg’ at all levels" without utilizing a looping mechanism (Note 13). An operation called the transitive closure of relations has been proposed to compute the recursive relationship as far as the recursion proceeds. 7.5.3 OUTER JOIN and OUTER UNION Operations Finally, we discuss some extensions of the JOIN and UNION operations. The JOIN operations described earlier match tuples that satisfy the join condition. For example, for
traditional file-processing systems: 1 Page 36 of 893 • • • • • Potential for enforcing standards. Reduced application development time. Flexibility. Availability of up-to-date information to all users. Economies of scale. Finally, we discussed the overhead costs of using a DBMS and discussed some situations in which it may not be advantageous to use a DBMS. Review Questions 1.1. Define the following terms: data, database, DBMS, database system, database catalog, programdata independence,
or the dominant entity type. Note 10 The weak entity type is also sometimes called the child entity type or the subordinate entity type. Note 11 The partial key is sometimes called the discriminator. Note 12 The rules in the miniworld that determine the constraints are sometimes called the business rules, since they are determined by the "business" or organization that will utilize the database. Note 13 In some notations, particularly those used in object modeling, the placing of the (min,
RESEARCH_ASSISTANT. A subclass with more than one superclass is called a shared subclass. For example, if every must be an ENGINEER but must also be a SALARIED_EMPLOYEE and a MANAGER, then ENGINEERING_MANAGER should be a shared subclass of all three superclasses (Figure 04.06). This leads to the concept known as multiple inheritance, since the shared subclass ENGINEERING_MANAGER directly inherits attributes and relationships from multiple classes. Notice that the existence of at least one shared