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', 'pqfi20ssea75m2idav5jn4t2b7', '216.73.216.147', '1751960098', '1751960098', '/product_info.php?info=p22_Plastic-tablecloth.html&XTCsid=adc8c520bddaa9e02a40df1e2a90f128')

[XT SQL Error]