Fix #79 - Added phrasing and slight reworking of sample code in G-7230 concerning public constants.

Author: kibeha

docs/4-language-usage/7-stored-objects/2-packages/g-7230.md

@@ -5,12 +5,14 @@
 
 ## Reason
 
-You should always declare package-level data inside the package body. You can then define "get and set" methods (functions and procedures, respectively) in the package specification to provide controlled access to that data. By doing so you can guarantee data integrity, you can change your data structure implementation, and also track access to those data structures. 
+You should always declare package-level data (non-constants) inside the package body. You can then define "get and set" methods (functions and procedures, respectively) in the package specification to provide controlled access to that data. By doing so you can guarantee data integrity, you can change your data structure implementation, and also track access to those data structures. 
 
-Data structures (scalar variables, collections, cursors) declared in the package specification (not within any specific program) can be referenced directly by any program running in a session with `execute` rights to the package. 
+Data structures (scalar variables, collections, cursors) declared in the package specification (not within any specific program) can be referenced directly by any program running in a session with `execute` rights to the package.
 
 Instead, declare all package-level data in the package body and provide "get and set" methods - a function to get the value and a procedure to set the value - in the package specification. Developers then can access the data using these methods - and will automatically follow all rules you set upon data modification.
 
+For package-level constants, consider whether the constant should be public and usable from other code, or if only relevant for code within the package. If the latter, declare the constant in the package body. If the former, it is typically good practice to place the constants in a package specification that only holds constants.
+
 ## Example (bad)
 
 ``` sql
@@ -42,6 +44,12 @@ end employee_api;
 ## Example (good)
 
 ``` sql
+create or replace package constants_up as
+   co_min_increase constant types_up.sal_increase_type := 0.01;
+   co_max_increase constant types_up.sal_increase_type := 0.5;
+end constants_up;
+/
+
 create or replace package employee_api as
    procedure set_salary_increase (in_increase in types_up.sal_increase_type);
    function salary_increase return types_up.sal_increase_type;
@@ -56,8 +64,8 @@ create or replace package body employee_api as
    procedure set_salary_increase (in_increase in types_up.sal_increase_type) is
    begin
       g_salary_increase := greatest(least(in_increase
-                                         ,constants_up.max_salary_increase())
-                                   ,constants_up.min_salary_increase());
+                                         ,constants_up.co_max_increase)
+                                   ,constants_up.co_min_increase);
    end set_salary_increase;
 
    function salary_increase return types_up.sal_increase_type is
@@ -68,7 +76,7 @@ create or replace package body employee_api as
    procedure init
    is
    begin
-      g_salary_increase := constants_up.min_salary_increase();
+      g_salary_increase := constants_up.co_min_increase;
    end init;
 begin
    init();