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', '56kli9rko7m946t92ojds2rcp5', '216.73.216.9', '1758197373', '1758197373', '/index.php?XTCsid=10a9616423dcd1c8172cd9709364165e')

[XT SQL Error]