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', 's72a6llfe2pu724jbgqurlj925', '216.73.216.139', '1763766827', '1763766827', '/index.php?XTCsid=72205775904d1a5c41b590dd7b5ff1d6&cat=c4_Beer-Mugs.html')

[XT SQL Error]