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', '859r755m8tle706kh1fcnrqcq6', '54.159.120.168', '1493248815', '1493248815', '/')

[XT SQL Error]