C H A P T E R 9
PL/SQL from SQL
Functions are an integral part of any well-designed PL/SQL application. They are an embodiment of programming best practices, such as code modularization, reuse, and the encapsulation of business or application logic. When used as simple building-blocks for larger programs, they can be an elegant and simple way to extend functionality while reducing code-complexity at minimal cost.
Conversely, when PL/SQL functions are heavily used, particularly in SQL statements, there can be a range of associated costs, most notably for performance. Depending on the nature of the function, simply calling PL/SQL from SQL and/or excessive I/O can degrade performance of even the most trivial of queries. ...