Oracle PL/SQL Programming: A Developer's Workbook

Chapter 27. External Procedures

As powerful as PL/SQL is, there are simply some things it cannot do because it’s locked inside the database. For example, there are many occasions where you might want to send an email (in an alert, for instance), perform some really complex mathematical functions (for example, an encryption system), or even just invoke a C library function. Fortunately, Oracle8 has a way to supplement the base PL/SQL language by allowing you to make calls to external libraries written in other languages, such as C. This chapter tests your understanding of this very advanced topic.

Beginner

27-1.	What is an external procedure in Oracle?
27-2.	Where can an external procedure be called in PL/SQL?
27-3.	True or false? Interprocess communication using external procedures requires about the same amount of complexity as using database pipes. The programmer can pass information to an external procedure, but the external program cannot yet pass information back. External procedures can be used as functions in SQL. While the most common language for external procedures is C, the code for an external procedure can be written in any language that can be compiled into a C-callable format. External procedures must be procedures; functions are not allowed. All that is required to execute an external procedure is the library itself and a PL/SQL wrapper. One extproc process is started per database. Oracle can call not only shared libraries, but any executable program. A CREATE LIBRARY statement ...