title: undefined error exception handling inpl/sql
body: <p>I am new to pl/sql programing. 
  I have an assignment :
  "Brewbean’s wants to add a check constraint on the QUANTITY column of the BB_BASKETITEM table. If a shopper enters a quantity value greater than 20 for an item, Brewbean’s wants to display the message “Check Quantity” onscreen. Using a text editor, open the assignment04-06.txt file in the Chapter04 folder. The first statement, ALTER TABLE, must be executed to add the check constraint. The next item is a PL/SQL block containing an INSERT action that tests this check constraint. Add code to this block to trap the check constraint violation and display the message."
  I tried,like this-</p>
  
  <pre><code>set serveroutput on;
  declare 
  ex_basket exception;
  pragma EXCEPTION_INIT(ex_basket, -02290);
  BEGIN
  ALTER TABLE bb_basketitem
    ADD CONSTRAINT bitems_qty_ck CHECK (quantity &lt; 20);
    INSERT INTO bb_basketitem 
     VALUES (88,8,10.8,21,16,2,3);
  exception
  when ex_basket then
  DBMS_OUTPUT.PUT_LINE('Check Quantity');
  END;
  </code></pre>
  
  <p>I got the error report like this:  </p>
  
  <blockquote>
    <p>ORA-06550: line 5, column 1:
    PLS-00103: Encountered the symbol "ALTER" when expecting one of the
    following:</p>
    
    <p>( begin case declare exit for goto if loop mod null pragma    raise
    return select update while with </p>
  </blockquote>
  
  <p>Sorry for this cheap question. I would love someone helping on this.</p>