Creating Procedures

In Oracle, you can create your own procedures.

The syntax for a procedure is:

CREATE [OR REPLACE] PROCEDURE procedure_name
    [ (parameter [,parameter]) ]

IS
    [declaration_section]

BEGIN
    executable_section

[EXCEPTION
    exception_section]

END [procedure_name];

When you create a procedure or function, you may define parameters. There are three types of parameters that can be declared:

1. IN - The parameter can be referenced by the procedure or function. The value of the parameter can not be overwritten by the procedure or function.
2. OUT - The parameter can not be referenced by the procedure or function, but the value of the parameter can be overwritten by the procedure or function.
3. IN OUT - The parameter can be referenced by the procedure or function and the value of the parameter can be overwritten by the procedure or function.

The following is a simple example of a procedure:

CREATE OR REPLACE Procedure UpdateCourse
   ( name_in IN varchar2 )
   
IS
   cnumber number;

   cursor c1 is
   select course_number
    from courses_tbl
    where course_name = name_in;

BEGIN

   open c1;
   fetch c1 into cnumber;

   if c1%notfound then
      cnumber := 9999;
   end if;
   
   insert into student_courses
   ( course_name,
     course_number )
   values ( name_in,
            cnumber );

   commit;

   close c1;

EXCEPTION
WHEN OTHERS THEN
   raise_application_error(-20001,'An error was encountered - '||SQLCODE||' -ERROR- '||SQLERRM);
END;

This procedure is called UpdateCourse. It has one parameter called name_in. The procedure will lookup the course_number based on course name. If it does not find a match, it defaults the course number to 99999. It then inserts a new record into the student_courses table.