3.1. Query Basics
In order to use functions, you need to know how to call them and how to construct their arguments. This section begins by explaining how the DUAL table allows you to use queries that don't involve a real table. Next, you'll learn about the ubiquitous NULL value and how it acts as a double-edged sword at times. Then we'll cover string literals and how to construct larger strings from one or more other strings and columns. Finally, you'll learn about numeric literals and operator precedence.
Once you know how to use the SELECT statement with the DUAL table, along with how string and numeric literals work, you'll be ready to explore the built-in functions. You'll see that they are potent tools to put into your DBA bag of tricks. ...
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