code: @Override
      protected boolean check4NullValues(final Connection _con,
                                         final String _tableName,
                                         final String _columnName)
          throws SQLException
      {
          boolean ret = true;
          final StringBuilder cmd = new StringBuilder();
          cmd.append("select count(*) from ").append(getTableQuote()).append(_tableName).append(getTableQuote())
                  .append(" where ").append(getColumnQuote()).append(_columnName).append(getColumnQuote())
                  .append(" is null");
  
          OracleDatabase.LOG.debug("    ..SQL> {}", cmd);
  
          final Statement stmt = _con.createStatement();
          ResultSet rs = null;
          try {
              rs = stmt.executeQuery(cmd.toString());
              rs.next();
              ret = rs.getInt(1) > 0;
          } finally {
              if (rs != null) {
                  rs.close();
              }
              stmt.close();
          }
          return ret;
      }
docs: {@inheritDoc}