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', '79ps13374chk1setv0f4dcann4', '216.73.216.9', '1758184165', '1758184165', '/index.php?XTCsid=e65207aee44f142683bacdd3544c84a8&cat=c4_Beer-Mugs.html')

[XT SQL Error]