Error in sql:

SELECT SQL_CALC_FOUND_ROWS * FROM conference WHERE (conference.site | 1 = conference.site) and status in ('online','closed') and date>=1970/01/01 and conference_id !=  and mail_type in (4) order by date asc limit 20

Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'and mail_type in (4) order by date asc limit 20' at line 1