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', 't617vqef8c4uqbkc37pmri1np1', '216.73.216.55', '1768404982', '1768404982', '/index.php?XTCsid=b2f2fd5328d88ea7ac143d7fb7715fbe')

[XT SQL Error]