Extension:CampaignEvents/ce participants table

mysql> describe ce_participants;
+----------------------------+---------------------+------+-----+---------+----------------+
| Field                      | Type                | Null | Key | Default | Extra          |
+----------------------------+---------------------+------+-----+---------+----------------+
| cep_id                     | bigint(20) unsigned | NO   | PRI | NULL    | auto_increment |
| cep_event_id               | bigint(20) unsigned | NO   | MUL | NULL    |                |
| cep_user_id                | int(10) unsigned    | NO   | MUL | NULL    |                |
| cep_private                | tinyint(1)          | NO   |     | NULL    |                |
| cep_registered_at          | binary(14)          | NO   |     | NULL    |                |
| cep_unregistered_at        | binary(14)          | YES  |     | NULL    |                |
| cep_first_answer_timestamp | binary(14)          | YES  |     | NULL    |                |
| cep_aggregation_timestamp  | binary(14)          | YES  |     | NULL    |                |
+----------------------------+---------------------+------+-----+---------+----------------+