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', '87s27a80ap4d46qfan9uteodf7', '18.234.88.196', '1558465241', '1558465241', '/lkw_plane_tasche_lkw_plane/product_info.php/info/p148')

[XT SQL Error]