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', '7odt2vfg30h4h95b185r8mr1u5', '216.73.216.40', '1763413663', '1763413663', '/xtshop/index.php?cat=c16_.html')

[XT SQL Error]