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', '61fo4cs4kq3f8egedtl3lp4dk0', '216.73.216.4', '1771222772', '1771222772', '/popup_content.php?XTCsid=0832187515ca706758d8e1ce01e34faf&coID=1')

[XT SQL Error]