Cursor ??

Jeg har dettee pl/sql script:

-- ***************
DECLARE

CURSOR c_order_numbers IS
      SELECT order_number
      FROM inactive_orders
      WHERE CUSTOMER_KEY = '1032';
     
      v_order_key varchar2(20);
 
BEGIN
    FOR v_order_number IN c_order_numbers
    LOOP
            dbms_output.put_line('order number' || v_order_number);

    END LOOP;   
END;
-- **************


Men få denne fejl meddelese:

The following error has occurred:

ORA-06550: line 13, column 26:
PLS-00306: wrong number or types of arguments in call to '||'
ORA-06550: line 13, column 5:
PL/SQL: Statement ignored



Hvad er det lige der er galt ???