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, http_referer) values ('', 'Guest', 'j88skcl11n7k85s9s2j81mie71', '172.17.0.19', '1455436444', '1455436444', '/shop/product_info.php?info=p1219_11-13-2013-KOPEK.html', '')

[XT SQL Error]