Cannot use BOOLEAN in Oracle

Question

Why we can't use BOOLEAN in SQL statement but we can use it in PL/SQL statement. But what does that mean? Thanks.

Answer 1

grus wrote:
Why we can't use BOOLEAN in SQL statement but we can use it in PL/SQL statement. But what does that mean? Thanks.As already explained, SQL and PL (Programming Logic) are different computer languages and have different data types. Though PL typically supports most SQL data types too.
Oracle however allows you to define your own SQL data types - and create these in a similar way as you would define an object orientated class. These data types have constructors, properties and methods, static class methods - and supports abstract definitions and inheritance. All the basics of an o-o class definition is supported.
This allows you to, for example, create your own boolean data type that you can use in both SQL and PL. Not that this is specifically a good idea for boolean values (as a single character column with a Y/N constraint can do the job equally well to). But even so, to define your own data types is a very powerful feature that can be used to deal with non-common data types in specialised database implementations.
An example of how to create a SQL boolean type was posted some time ago in [this thread|http://forums.oracle.com/forums/thread.jspa?messageID=2116991#2116991].