桌子：

**timeslot**:
----------
id_timeslot   times
1             09:00
2             09:30
3             10:00
4             10:30
5             11:00

**bookslot**
id   id_timeslot     date        b_ref
-------------------------------------------
1    2               2010-02-22  001 
2    3               2010-02-22  001
3    4               2010-02-22  001
4    5               2010-02-22  001
5    2               2010-02-25  002
6    3               2010-02-27  003
7    4               2010-02-27  003
8    5               2010-02-27  003

的PHP

$q = $mysqli->query("SELECT * FROM bookslot  
LEFT JOIN timeslot ON bookslot.id_timeslot = timeslot.id_timeslot   
WHERE bookslot.status = 1 
GROUP BY bookslot.b_ref  
ORDER BY bookslot.date ASC, bookslot.id_timeslot ASC LIMIT 20");

HTML结果：

DATE         TIMES  
2010-02-22   10:30
2010-02-25   09:30
2010-02-27   11:00

任何人都注意到桌上的结果。时代是不正确的顺序？
我改变了另一种方式与ASC / DESC，仍然显示最后一个id_timeslot的时间吗？

预期结果：

DATE         TIMES  
2010-02-22   09:30
2010-02-25   09:30
2010-02-27   10:00