Advanced Oracle PL/SQL Programming with Packages

1.2. What Are the Types and Layers of Packages?

Although any PL/SQL package must have the same structure and follow the same rules, there are different types of packages that will play different roles in your application.

Types of Package	Description
Builtin	A builtin package is provided to you by Oracle Corporation, built right into the PL/SQL language as installed. (A builtin package could reside in the database as stored code or could instead be imbedded in a client tool, such as Oracle Developer/2000.)
Prebuilt	Prebuilt packages are libraries of packages that are built by third parties or other developers that are installed in and used by your PL/SQL environment.
Build-Your-Own (BYO)	The very best kind of package: the one you build yourself, or is built by your application development team.

Figure 1.1 shows how these different types of packages interact as layers of PL/SQL code and packages that are available to you. We describe the types further in "Types of Packages" later in this chapter.

Figure 1.1. The layers of PL/SQL code and packages

The lowest layer of code upon which you build your PL/SQL applications is the SQL language. PL/SQL was designed explicitly as a procedural language extension to SQL; most of your PL/SQL programs will function as an interface between a user of some kind and the database.

The next layer of code is the core PL/SQL language. At the center of the ...