Appendix K. A Brief Introduction to Number Systems, Boolean Algebra, and Set Theory

We believe strongly that daily users of an RDBMS and SQL will greatly benefit from understanding the basics of discrete math and set theory that serve as the foundation for SQL.

You don't need a math degree to write and read SQL code, but the knowledge of how binary and hexadecimal numbers are different from decimals and how they can be converted to each other can help you to understand better the issues directly related to it. Such issues include security, data encryption, data storage principles, and the Oracle ROWID data type — to mention just a few.

Understanding set theory is even more important. Basically, the result of any database query is a set of values, so it would benefit you immediately to know the rules of working with sets to create efficient queries.

The Number Systems

The decimal number system we casually use in our everyday lives is not the only number system in the world. Most of us are used to the decimal system, take it for granted, and maybe even consider it the only possible collection of numbers, but that assumption is valid only if we are talking about modern humans. Machines don't use the decimal system. Moreover, humans themselves, now and in the past, have used other systems. For example, the ancient civilization of Sumerians used a base-sixty number system six thousand years ago; that is, they had 60 different characters to represent digits. In our own time, the English word ...

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