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', 'k2utfgjq7dk76s6pcc71k995n4', '216.73.216.165', '1752307592', '1752307592', '/index.php?cat=c6_Foodstuffs.html&XTCsid=0920dd1f7934388b33528580c92ca640')

[XT SQL Error]