title: Can't delete foreign key (Oracle)
body: <p>I'm trying to delete all foreign keys of a table. First I get all the names of those keys using <code>meta.getExportedKeys(null, null, table);</code> and <code>rs.getString("FK_NAME")</code>.</p>
  
  <p>But when I try to delete this key using:</p>
  
  <pre><code>ALTER TABLE tablename DROP CONSTRAINT fkname
  </code></pre>
  
  <p>it only works for some keys. Sometimes I'm getting:</p>
  
  <pre><code>ORA-02443: Cannot drop constraint - nonexistent constraint
  </code></pre>
  
  <p>But the foreign key is definitely there. What am I doing wrong?</p>