SQLPLUS object system. is invalid - oracle

Question

I'm stuck with some simple procedure and I can't figure out why.
This is my code, which I'm running in sqlplus:
CREATE OR REPLACE PROCEDURE NormalizeName(fullname IN NVARCHAR2)
IS
BEGIN
SELECT TRIM(fullname) INTO fullname FROM DUAL;
DBMS_OUTPUT.PUT_LINE(fullname);
END NormalizeName;
/
BEGIN
NormalizeName('Alice Wonderland ');
END;
/
When I run it, I get the error:
Warning: Procedure created with compilation errors.
NormalizeName('Alice Wonderland ');
*
ERROR at line 2:
ORA-06550: line 2, column 2:
PLS-00905: object SYSTEM.NORMALIZENAME is invalid
ORA-06550: line 2, column 2:
PL/SQL: Statement ignored
What's wrong?

Answer 1

1) Never create objects in the SYS or SYSTEM schema. Those are reserved for Oracle. If you want to create objects, create a new schema first.
2) When you see that a procedure has been created with compilation errors in SQL*Plus, type show errors to see the errors.
3) The error appears to be that your SELECT statement is trying to write to the fullname parameter. But that parameter is defined as an IN parameter, not IN OUT, so it is read-only. If you define the parameter as IN OUT, though, you could not pass a string constant to the procedure, you'd need to define a local variable in your calling block. It doesn't make a lot of sense to have a procedure that doesn't do anything other than call dbms_output since there is no guarantee that anyone will see the data written to that buffer. My guess is that you really want a function that returns a normalized name. Something like
CREATE OR REPLACE FUNCTION NormalizeName( p_full_name IN VARCHAR2 )
RETURN VARCHAR2
IS
BEGIN
RETURN TRIM( p_full_name );
END;
which you can then call
DECLARE
l_normalized_name VARCHAR2(100);
BEGIN
l_normalized_name := NormalizeName( 'Alice Wonderland ' );
dbms_output.put_line( l_normalized_name );
END;
If you really need a procedure because this is a homework assignment
CREATE OR REPLACE PROCEDURE NormalizeName( p_fullname IN VARCHAR2 )
AS
BEGIN
dbms_output.put_line( TRIM( p_fullname ));
END;
In the real world, you should only be using procedures when you want to manipulate the state of the database (i.e. you're doing INSERT, UPDATE, DELETE, MERGE, etc.). You use functions when you want to perform calculations without changing the state of the database or when you want to manipulate data passed in parameters.