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', '54utfrip5g8mtijst7ee3gq902', '216.73.216.244', '1752211228', '1752211228', '/popup_content.php?coID=1&XTCsid=81fba26e1f006e30d12d9ee4d58a4030')

[XT SQL Error]