mysql左连接，mysql做内连接？

Question

我想做一个左连接但是mysql只做一个内连接？ 我的查询有什么问题？

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只给那些有相应约会的avhours

提前致谢！

Answer 1

由于这些条件：

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

您只从tbl_appointment中选择非null 。

如果这是你想要的 - 将它们移动到左连接的ON部分