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', '7s6un1egti8hdd4fprs2atb894', '216.73.216.119', '1758130762', '1758130762', '/xtshop/index.php?cat=c103_.html')

[XT SQL Error]