Mine

mysql> select * from corfu44_reservations;+----+--------+-----------+-------+---------------------+---------------------+-------------+-----------+----------+--------+--------+----------+-------------+-------------+| id | car_id | client_id | agent | start_datetime      | end_datetime        | start_place | end_place | contract | price1 | price2 | babyseat | boosterseat | remarks     |+----+--------+-----------+-------+---------------------+---------------------+-------------+-----------+----------+--------+--------+----------+-------------+-------------+|  7 |      1 |         1 | agent | 2011-04-11 00:00:00 | 2011-04-16 00:00:00 |             |           | test     | 10     | 20     | yes      | yes        | test remark |+----+--------+-----------+-------+---------------------+---------------------+-------------+-----------+----------+--------+--------+----------+-------------+-------------+1 row in set (0.00 sec)mysql> SELECT id FROM corfu44_reservations WHERE (str_to_date('2011-04-11 10:00:00','%Y-%c-%d %H:%i:%s') BETWEEN start_datetime AND end_datetime) OR (str_to_date('2011-04-12 12:00:00','%Y-%c-%d %H:%i:%s') BETWEEN start_datetime AND end_datetime) AND car_id = 1    -> ;+----+| id |+----+|  7 |+----+1 row in set (0.00 sec)