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', 'lgb12f7sjsh25n4a7tlsufe1h3', '18.97.9.172', '1750671375', '1750671375', '/xtshop/index.php?cat=c44_.html')

[XT SQL Error]