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', 'pgr2opcjfbnr8oero1r7u0ihd1', '216.73.216.147', '1751840942', '1751840942', '/index.php?XTCsid=ac1369b23120edf0063ec4033ff02fe6')

[XT SQL Error]