I was looking at a 3rd party application running in an Oracle 11.2 database. I listed the source code of one of the packages and noticed that it contained 5 versions of the same procedure. I have never done any Oracle development so I am not a PL/SQL expert and this seemed strange to me at first. Then I thought about what I have been learning about Java recently and realized that this was Oracle doing overloading. This allows more than one procedure to have a given name as long as each version has a different set of parameters. Oracle then chooses the appropriate version based on the parameters supplied. You can see what I mean in the example below. A package is created called PACKAGE1. It contains two versions of a procedure called PROCEDURE1. Each version displays the parameters supplied to it. So, if you supply 1 parameter, Oracle chooses to run the version which accepts (and displays) 1 parameter. Conversely, if you supply 2 parameters, Oracle selects the version which accepts (and displays) 2 parameters:
SQL> set serveroutput on
SQL> create or replace package package1 is
2 procedure procedure1
3 (parameter1 in number);
4 procedure procedure1
5 (parameter1 in number,
6 parameter2 in number);
7 end package1;
8 /
Package created.
SQL> create or replace package body package1 is
2 procedure procedure1
3 (parameter1 in number)
4 is
5 begin
6 dbms_output.put_line('parameter1 = '||parameter1);
7 end;
8 procedure procedure1
9 (parameter1 in number,
10 parameter2 in number)
11 is
12 begin
13 dbms_output.put_line('parameter1 = '||parameter1);
14 dbms_output.put_line('parameter2 = '||parameter2);
15 end;
16 end package1;
17 /
Package body created.
SQL> exec package1.procedure1(1);
parameter1 = 1
PL/SQL procedure successfully completed.
SQL> exec package1.procedure1(1,2);
parameter1 = 1
parameter2 = 2
PL/SQL procedure successfully completed.
SQL>
