Built-in functions for opaque data types

The database server provides special SQL-invoked functions, called built-in functions, that provide some basic mathematical operations. The built-in functions that the database server provides handle the built-in data types. You can overload a built-in function to provide the associated operation on your new opaque data type. If you overload a built-in function, follow these rules:

1. The name of the built-in function must match the name listed in Built-in functions that you can overload. However, the name is not case sensitive; the abs() function is the same as the Abs() function.
2. The built-in function must be one that can be overridden.
3. The built-in function must handle the correct number of parameters, and these parameters must be of the correct data type.
4. The built-in function must return the correct data type, where appropriate.