Oracle PL/SQL Programming, 5th Edition

The BOOLEAN Datatype

Boolean values and variables are very useful in PL/SQL. Because a Boolean variable can only be TRUE, FALSE, or NULL, you can use that variable to explain what is happening in your code. With Booleans you can write code that is easily readable because it is more English-like. You can replace a complicated Boolean expression involving many different variables and tests with a single Boolean variable that directly expresses the intention and meaning of the text.

Here is an example of an IF statement with a single Boolean variable (or function—you really can’t tell the difference just by looking at this short bit of code):

IF report_requested
THEN
   print_report (report_id);
END IF;

The beauty of this technique is that it not only makes your code a bit more self-documenting, it also has the potential to insulate your code from future change. For example, consider the human interface that needs to precede the previous code fragment. How do you know that a report was requested? Perhaps you ask the user to answer a question with a Y or an N, or perhaps the user must place a check in a checkbox or select an option from a drop-down list. The point is that it doesn’t matter. You can freely change the human interface of your code, and, as long as that interface properly sets the report_requested Boolean variable, the actual reporting functionality will continue to work correctly.

Note

While PL/SQL supports a Boolean datatype, the Oracle database does not. You can create and work ...