MembersModel:
    public $hasAndBelongsToMany = array(
        'Event' => array(
            'className' => 'Event',
            'unique' => 'keepExisting',
            'conditions' => array('Event.course_id'=>null),
        )
    );

Produces error:

Database Error
Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Event.course_id' in 'where clause'

SQL Query: SELECT `EventsMember`.`event_id`
FROM `eventsa7_esa`.`events_members` AS `EventsMember`
WHERE `EventsMember`.`member_id` = 12 AND `Event`.`course_id` IS NULL



I think it should produce this SQL instead (notice additional 3rd line):
SELECT `EventsMember`.`event_id`
FROM `eventsa7_esa`.`events_members` AS `EventsMember`,
`eventsa7_esa`.`events` AS `Event`
WHERE `EventsMember`.`member_id` = 12
AND `Event`.`course_id` IS NULL

The code works in SQLite when the MembersModel says:
'conditions' => array('course_id'=>null),
But does not work in MySQL.