PL/SQL User's Guide and Reference

The Package Body

The package body implements the package specification. That is, the package body contains the definition of every cursor and subprogram declared in the package specification. Keep in mind that subprograms defined in a package body are accessible outside the package only if their specifications also appear in the package specification.

To match subprogram specifications and bodies, PL/SQL does a token-by-token comparison of their headers. So, except for white space, the headers must match word for word. Otherwise, PL/SQL raises an exception, as the following example shows:

CREATE PACKAGE emp_actions AS
   ...
   PROCEDURE calc_bonus (date_hired emp.hiredate%TYPE, ...);
END emp_actions;
 
CREATE PACKAGE BODY emp_actions AS
   ...                           
   PROCEDURE calc_bunus (date_hired DATE, ...) IS 
      -- parameter declaration raises an exception because 'DATE'
      -- does not match 'emp.hiredate%TYPE' word for word
   BEGIN
      ...
   END calc_bonus;
END emp_actions;

The package body can also contain private declarations, which define types and objects necessary for the internal workings of the package. The scope of these declarations is local to the package body. Therefore, the declared types and objects are inaccessible except from within the package body. Unlike a package specification, the declarative part of a package body can contain subprogram bodies.

Following the declarative part of a package body is the optional initialization part, which typically holds statements that initialize some of the variables previously declared in the package.

The initialization part of a package plays a minor role because, unlike subprograms, a package cannot be called or passed parameters. As a result, the initialization part of a package is run only once, the first time you reference the package.

Recall that if a specification declares only types, constants, variables, and exceptions, the package body is unnecessary. However, the body can still be used to initialize objects declared in the specification.