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', '1m3541hq31sbf3fim14qk0qbm3', '216.73.216.147', '1751960648', '1751960648', '/products_new.php?XTCsid=c407ede434192d8d024c7c2f06b2be8c')

[XT SQL Error]