title: trying to add an agent (not allowing duplicate last names). Initial total sales should be zero
body: <p>I am receiving the following error when trying to compile and execute. I am having issues how to figure this out.
  14/7      PL/SQL: Statement ignored
  14/10     PLS-00204: function or pseudo-column 'EXISTS' may be used inside a SQL statement only
  Errors: check compiler log</p>
  
  <pre><code>    CREATE OR REPLACE PROCEDURE AddAgent(
      p_Agent_Fname IN Agent.Agent_Fname%TYPE,
      p_Agent_Lname IN Agent.Agent_Lname%TYPE,
      p_Agent_Address IN Agent.Agent_Address%TYPE,
      p_Agent_Tsales IN Agent.Agent_Tsales%TYPE,
      p_Agent_Salary IN Agent.Agent_Salary%TYPE)
  
  IS
          p_ErrorCode number;     --USED FOR ERROR CHECKING
          p_ErrorMsg  Varchar2(200);
          p_CurrentUser Varchar2(100);
  BEGIN
  
    IF EXISTS 
    (SELECT * FROM Agent WHERE Agent_Lname = p_Agent_Lname) THEN
  
        dbms_output.put_line('Failure');    
    ELSE
       INSERT INTO Agent (Agent_Fname, Agent_Lname, Agent_Address, Agent_Tsales, Agent_Salary) 
       SELECT p_Agent_Fname, p_Agent_Lname, p_Agent_Address, 0, p_Agent_Salary
       from Dual;
       COMMIT;
  
       dbms_output.put_line('Success');
      END IF;
  END;
  </code></pre>