Objects created within a database are not cast in stone. The ability to easily change database objects gives an RDBMS a big advantage over nonrelctional models because flexibility is built into the relational database concept. This includes the ability to create, modify, and destroy database objects. Needless to say, all our three major vendors provide this ability so as to incur minimal impact on other database entities.
Examples in this chapter assume incremental buildup of the ACME database started in Chapter 4. Constraints implemented in the database scripts included with the CD-ROM may prevent some of the statements from successful execution.