Where the set value come from

Question

where is the set value come from, can the value come from Servlet
create or replace
PACKAGE BODY TRIGGER_test as
function setStudentNum(sn in varchar2) return varchar2 as
Begin
  staff_num := sn;
  return ('Success');
Exception
When OTHERS then
  return ('Error');
End setStudentNum;
function getStudentNum return varchar2 as
Begin
  if (staff_num is not null) then
   return (staff_num);
  else
   return ('undefine');
  end if;
End getStudentNum;
end TRIGGER_test;

Answer 1

Hjava wrote:
>i am assuming that the function trigger_test.setStudentNum() gets executed first which will initialize the staff_num variabl
when and how?
Some 'other' bit of code somewhere.  How do we know, as we don't have your application/process code.  There will be something somewhere that calls the setStudentName function, so that when the getStudentName function is called it can return a value.  Values don't just magically appear.
The only time there may be some code that initializes a value (other than in the declaration of the variable itself) is in a package body execution section e.g.
SQL> create or replace PACKAGE TRIGGER_test as
  2    function setStudentNum(sn in varchar2) return varchar2;
  3    function getStudentNum return varchar2;
  4  end TRIGGER_test;
  5  /
Package created.
SQL> create or replace PACKAGE BODY TRIGGER_test as
  2    staff_num varchar2(30);
  3    function setStudentNum(sn in varchar2) return varchar2 as
  4    Begin
  5      staff_num := sn;
  6      return ('Success');
  7    End setStudentNum;
  8
  9    function getStudentNum return varchar2 as
10    Begin
11      return (staff_num);
12    End getStudentNum;
13  begin
14    staff_num := 'undefined';
15  end TRIGGER_test;
16  /
Package body created.
SQL> select trigger_test.getStudentNum() from dual;
TRIGGER_TEST.GETSTUDENTNUM()
undefined
SQL> select trigger_test.setStudentNum('1234') from dual;
TRIGGER_TEST.SETSTUDENTNUM('1234')
Success
SQL> select trigger_test.getStudentNum() from dual;
TRIGGER_TEST.GETSTUDENTNUM()
1234
As you can see, the first time the package is instantiated in memory (the first time we call any function in it), the package body execution section is called which sets the variable to "undefined" in this example, before the function itself is called to return what the value is.