Join between a collection and a table - oracle

Question

I have a problem with procedures in PL/SQL. I have a public procedure declared in a package and I want to call another procedure(private) inside the first one.
PROCEDURE show_notesforstudent (number_id IN number) as
...
DBMS_OUTPUT.PUT_LINE('The notes for the student with number_id X are: '|| Y);
DBMS_OUTPUT.PUT_LINE('here is the call for the private procedure');
erase_student(number_id);
END;
This code is a general example, my code is bigger and I can't put it all here. Here is only the main idea.
For this call I face this error: "Error(31,5): PLS-00313: 'erase_student' not declared in this scope".
The implementation of erase_student procedure is:
PROCEDURE erase_student(n_id students.number_id%type) AS
student_inexistent EXCEPTION;
PRAGMA EXCEPTION_INIT(student_inexistent, -20002);
counter integer;
BEGIN
SELECT COUNT(nmber_id) INTO counter FROM studens where number_id = n_id;
IF counter = 0 THEN
raise student_inexistent;
END IF;
DELETE FROM students WHERE number_id = n_id;
EXCEPTION
WHEN student_inexistent THEN
raise_application_error (-20002, 'Student with number_id' || n_id || ' doesn't exists in database');
END stergere_student;`

Answer 1

Lets simplify your code and make it syntactically correct:
CREATE OR REPLACE PACKAGE package_name
AS
PROCEDURE show_notesforstudent (number_id IN number);
END;
/
CREATE OR REPLACE PACKAGE BODY package_name
AS
PROCEDURE show_notesforstudent (number_id IN number)
AS
BEGIN
erase_student(number_id);
END;
PROCEDURE erase_student(n_id NUMBER) AS BEGIN NULL; END;
END;
/
However, it still won't compile as we get PLS-00313: 'ERASE_STUDENT' not declared in this scope. It can be fixed by re-organising the package to ensure that the private procedure is declared before it is called; like this:
CREATE OR REPLACE PACKAGE BODY package_name
AS
PROCEDURE erase_student(n_id NUMBER) AS BEGIN NULL; END; -- Header and body
PROCEDURE show_notesforstudent (number_id IN number)
AS
BEGIN
erase_student(number_id);
END;
END;
/
However, if you want to keep the order of the procedures in the package then you could just use a forward declaration to declare the header for the private procedure before it is called and declare the body afterwards; like this:
CREATE OR REPLACE PACKAGE BODY package_name
AS
PROCEDURE erase_student(n_id NUMBER); -- Header only
PROCEDURE show_notesforstudent (number_id IN number)
AS
BEGIN
erase_student(number_id);
END;
PROCEDURE erase_student(n_id NUMBER) AS BEGIN NULL; END; -- Header and body
END;
/