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', 'eg6af9gfts2l5uddcger4g3dd2', '216.73.216.122', '1767803147', '1767803147', '/index.php?XTCsid=a8f768c639dfd62c2d6d3cd7ed21b720&language=en')

[XT SQL Error]