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', 'hm13nhlp4pd1o8vdrd5s8ubq32', '216.73.216.99', '1761905216', '1761905216', '/index.php?XTCsid=6c2468ca28c6c182aaed37353d32ae32&cat=c6_Foodstuffs.html')

[XT SQL Error]