1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', 'a4vjn95ufapgjvde95vjno0qn4', '216.73.216.185', '1752883100', '1752883100', '/popup_content.php?coID=1&XTCsid=38f09672db884903e3803adf9d076819')

[XT SQL Error]