SQL For Dummies®, 7th Edition

Chapter 14. Protecting Data

Everyone has heard of Murphy's Law — usually stated, "If anything can go wrong, it will." People joke about this pseudo-law because most of the time things go fine. At times, you may feel lucky because you're untouched by what purports to be one of the basic laws of the universe. When unexpected problems arise, you probably just recognize what has happened and deal with it.

In a complex structure, the potential for unanticipated problems shoots way up (a mathematician might say it "increases approximately as the square of the complexity"). Thus large software projects are almost always delivered late and are often loaded with bugs. A nontrivial, multiuser DBMS application is a large, complex structure. In the course of operation, many things can go wrong. Methods have been developed for minimizing the impact of these problems, but the problems can never be eliminated completely. This is good news for professional people who do database maintenance and repair — because automating them out of a job will probably never be possible. This chapter discusses the major things that can go wrong with a database — and the tools that SQL provides for you to deal with the problems that arise.

Threats to Data Integrity

Cyberspace (including your network) is a nice place to visit, but for the data living there, it's no picnic. Data can be damaged or corrupted in a variety of ways. Chapter 5 discusses problems resulting from bad input data, operator error, and deliberate ...