mysql左连接，MySQL做内连接？

Question

我想做一个左连接，但mysql只是做一个内部连接？ 我的查询有什么不对？

select av.*, ap.* 
from tbl_available av 
left join tbl_appointment ap 
on av.avHours = ap.appointmenttime 
where av.avCalendarId = 2 
and (ap.calendarid = 2 or ap.calendarid= null) 
and (ap.appointmentdate = "2012-10-01" or ap.appointmentdate = null) 
and av.avDays = DayOfweek("2012-10-01") 
order by avHours 

MySQL只给那些谁拥有相应提前预约

感谢avHours！

Answer 1

由于这些条件的：

and ap.calendarid = 2 
and ap.appointmentdate = "2012-10-01" 

你tbl_appointment只能选择行不属于null。

如果这就是你想要的东西 - 它们移动到左连接的ON部分