FUNDAMENTALS OF DATABASE SYSTEMS 6TH EDITION SOLUTION MANUAL

We must carefully consider the problems associated with nulls when designing a relational database schema. There is no fully satisfactory relational design theory as yet that includes null values. One problem occurs when some tuples have null values for attributes that will be used to JOIN[r]

Rules that specify actions that are automatically triggered by certain events have been considered as important enhancements to a database system for quite some time. In fact, the concept of triggers —a technique for specifying certain types of active rules—has existed in ear[r]

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In some cases a particular entity may not have an applicable value for an attribute. For example, the ApartmentNumber attribute of an address applies only to addresses that are in apartment buildings and not to other types of residences, such as single-family homes. Similarly, a Coll[r]