11.9. Types

11.9.1. Boolean

You can declare a BOOLEAN PL/SQL variable type. There is no BOOLEAN database column type.

Booleans are easy to work with. Often the existence of a value logically relates to a Boolean variable. For the student's demo, a student can have several majors (e.g., Biology). One valid lookup value is: Undeclared. Suppose you consider Undeclared to be FALSE and any other major to be TRUE. Logically this equates to: having a major is TRUE. Having an undeclared major is false. Such a scenario can be common in application code.

It helps to have a package that maps Boolean values to a 1 and 0. For example, the following package is a general purpose package that transforms a Boolean to and from a zero or one.

 CREATE OR REPLACE ...

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