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', '19hug4bhub20g8br7uibcah8r3', '216.73.216.9', '1758204848', '1758204848', '/shop_content.php?XTCsid=0832187515ca706758d8e1ce01e34faf&coID=3&language=de')

[XT SQL Error]