From: http://eventsmanagerpro.com/support/questions/printcsv-printexport-the-transaction-no-and-transaction-date/

  $results = $wpdb->get_results("SELECT * FROM ".EM_TRANSACTIONS_TABLE." WHERE booking_id='".$EM_Booking->booking_id."'", ARRAY_A);
  foreach ($results as $result){
    echo $results['transaction_id']; //this is the transaction id for example
  }
  
  

From: http://eventsmanagerpro.com/support/tickets/export-total-transaction-amount/

total transaction amount by adding a new exportable column.

  /**
  * Adds columns in the bookings tables
  * @param array $template
  * @param EM_Bookings_Table $EM_Bookings_Table
  * @return string
  */
  function my_em_bookings_table_cols_template($template, $EM_Bookings_Table){
    $template['transaction_price'] = 'TXN Price';
      return $template;
  }
  add_action('em_bookings_table_cols_template', 'my_em_bookings_table_cols_template',10,1);

  /**
  * @param string $val
  * @param string $col
  * @param EM_Booking $EM_Booking
  */
  function my_em_custom_booking_form_cols_txn_price($val, $EM_Booking){
          global $wpdb;
    $var = $wpdb->get_var('SELECT transaction_total_amount FROM '.EM_TRANSACTIONS_TABLE.' WHERE booking_id='.$EM_Booking->booking_id);
      return em_get_currency_formatted($var);
  }
  add_filter('em_bookings_table_rows_col_transaction_price','my_em_custom_booking_form_cols_txn_price', 10, 3);