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', '1gbc3fn58ohkl4ucs14tualik5', '216.73.216.9', '1758160226', '1758160226', '/index.php?XTCsid=d163dd0fc0b54bf3066f85422c77e00a&cat=c4_Beer-Mugs.html')

[XT SQL Error]