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', 'us4735knr24cvg70su6jd4t6i7', '216.73.216.121', '1761801043', '1761801043', '/index.php?XTCsid=ff3f9099e440e42e7d3b08f73df08c38')

[XT SQL Error]