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', 'cl3n5s2u1chbbr25uva63o3ep4', '52.14.187.136', '1746761549', '1746761549', '/xtshop/index.php?cat=c44_.html')

[XT SQL Error]