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', '4nu89p0tj3it2v9dmitgg9ctu0', '216.73.216.9', '1758149767', '1758149767', '/index.php?XTCsid=3e3fcef0642c69bbf707de3c0bc1cf9c&cat=c5_Crockery.html')

[XT SQL Error]