PL/SQL Function to convert fields & set max length

Question

I am having a problem with the following assignment:
Write a stored PL-SQL function called namefct that will convert two varchar2 fields (first and last names) into the format: lastname, firstname with a maximum length of 10 chars. If the combined size of the two names is greater than 10 characters, you will issue an error message indicating the name has been shortened to 10 characters and return only the first ten characters, otherwise return the entire name. Test the namefct function by using the staff table created in Part 1 (above). Turn in: the SQL statements to build the function, execute the sample code and the resulting output.
This is the start of my attempt, excluding the error message that is to be issued:
CREATE OR REPLACE FUNCTION namefct (fname VARCHAR2, lname VARCHAR2) IS
BEGIN
column "full name" format a10;
SELECT namefct(fname, lname) as "full name" from staff;
END namefct
Any advice or assistance would be greatly appreciated, since my Professor seems unwilling to assist me. Thanks!

Answer 1

Write a stored PL-SQL function called namefct that
will convert two varchar2 fields (first and last
names) into the format: lastname, firstname with a
maximum length of 10 chars. If the combined size of
the two names is greater than 10 characters, you will
issue an error message indicating the name has been
shortened to 10 characters and return only the first
ten characters, otherwise return the entire name.
Test the namefct function by using the staff table
created in Part 1 (above). Turn in: the SQL
statements to build the function, execute the sample
code and the resulting output.Firstly you need to consider what you have already been taught as you need to ensure that you code your function according to the purpose of the assignment. i.e. are you supposed to be demonstrating the use of returning values in a function or are you supposed to be demonstrating the use of exception handling etc.
The main tricky bit with this assignment is the requirement to show an error message and still return a value. If you were to just raise an exception with the error message (e.g. raise application error) then you won't be able to actually return a value. Because it's a function and not a procedure that has been specified you aren't returning the value in an OUT parameter which would have made passing the value back and raising an exception easier.
So, the only real way to have a function and allow it to show an error message would be something like...
SQL> ed
Wrote file afiedt.buf
  1  CREATE OR REPLACE FUNCTION f_name(p_forename IN VARCHAR2, p_surname IN VARCHAR2) RETURN VARCHAR2 IS
  2    name_too_long EXCEPTION;
  3  BEGIN
  4    IF LENGTH(p_surname||', '||p_forename) > 10 THEN
  5      RAISE name_too_long;
  6    END IF;
  7    RETURN p_surname||', '||p_forename;
  8  EXCEPTION
  9    WHEN name_too_long THEN
10      DBMS_OUTPUT.PUT_LINE('Name Too Long. Truncating to 10 chrs.');
11      RETURN SUBSTR(p_surname||', '||p_forename, 1, 10);
12* END;
SQL> /
Function created.
SQL> select f_name('FRED','SIMS') from dual;
F_NAME('FRED','SIMS')
SIMS, FRED
SQL> select f_name('FRED','SIMKINSON') from dual;
F_NAME('FRED','SIMKINSON')
SIMKINSON,
Name Too Long. Truncating to 10 chrs.
SQL>Note: Tutors/Professors are very wise to checking your work on the internet to make sure it hasn't been copied, so I would suggest you don't just copy this verbatim, but actually read it and understand how it's working and write your own version, taking account of what you have been taught so far and not using things you haven't been taught.
;)