title: Drop foreign-key constraint
body: <p>How to drop a foreign key if I have not named it during creation</p>
  
  <pre><code>create table abc(
  id number(10),
  foreign key (id) references tab(roll)
  );
  </code></pre>
  
  <p>even</p>
  
  <pre><code> alter table abc drop foreign key mn_ibfk_1;
  </code></pre>
  
  <p>is not working for me. I am using Oracle 10g.</p>