Advanced Oracle PL/SQL Programming with Packages

1.1. What Is a PL/SQL Package?

A package is a collection of PL/SQL elements that are "packaged" or grouped together within a special BEGIN-END syntax, a kind of "meta-block." Here is a partial list of the kinds of elements you can place in a package:

• Cursors

• Variables (scalars, records, tables, etc.) and constants

• Exception names and pragmas for associating an error number with an exception

• PL/SQL table and record TYPE statements

• Procedures and functions

Packages are among the least understood and most underutilized features of PL/SQL. That's a shame because the package structure is also one of the most useful constructs for building well-designed PL/SQL-based applications. Packages provide a structure to organize your modules and other PL/SQL elements. They encourage proper structured programming techniques in an environment that often befuddles the implementation of structured programming. When you place a program unit into a package you automatically create a "context" for that program. By collecting related PL/SQL elements in a package, you express that relationship in the very structure of the code itself. Packages are often called "the poor man's objects" because they support some, but not all, object-oriented rules.

The PL/SQL package is a deceptively simple, yet powerful construct. It consists of up to two distinct parts: the specification and the body.

• The package specification, which defines the public interface (API) of the package: those elements that can be referenced ...