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', 'epdt1toq11acobj95fnptti7o0', '216.73.216.9', '1758108188', '1758108188', '/index.php?XTCsid=e786190734d0d1381d87ecc8370dc449&cat=c2_Dekoration.html')

[XT SQL Error]