title: Full Outer Join not flagging errors with incorrect output in Oracle
body: <p>I am trying to implement a full outer join query that displays all customers and staff and their sum of all their purchases. It is running without throwing any errors, however, the aggregate sum function isn't working. Only the N/A is being printed, no review scores are in the output. </p>
  
  <pre><code>SELECT CUSTOMER.C_NAME, STAFF.E_NAME, DECODE(SUM(CUSTOMER.PRICE),
                                      NULL, 'N/A') AS BILL
  FROM CUSTOMER
  FULL OUTER JOIN STAFF
  ON CUSTOMER.C_NAME = STAFF.E_NAME
  group by CUSTOMER.C_NAME, E_NAME
  order by CUSTOMER.C_NAME, E_NAME; 
  </code></pre>
  
  <p>I want to understand s happening to make this query problematic.</p>