-- Connect programmer/p@9i

set serveroutput on;  

drop function Get_Grade_Description;

create or replace function Get_Grade_Description(grade IN VARCHAR2) RETURN VARCHAR2 is

  description VARCHAR2(15);
begin
  -- use a CASE Expression to store the description for
  -- the grade in a variable
  description := CASE grade
                   WHEN 'A' THEN 'Excellent'

                   WHEN 'B' THEN 'Very Good'
                   WHEN 'C' THEN 'Good'
                   WHEN 'D' THEN 'Fair'
                   WHEN 'F' THEN 'Fail'
                   ELSE 'No such grade'
                 END;
  -- return the description

  return description;
end Get_Grade_Description;
/
Show Errors

select Get_Grade_Description('A') from dual
/