mysql左連接，mysql做內連接？

Question

我想做一個左連接但是mysql只做一個內連接？ 我的查詢有什么問題？

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只給那些有相應約會的avhours

提前致謝！

Answer 1

由於這些條件：

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

您只從tbl_appointment中選擇非null 。

如果這是你想要的 - 將它們移動到左連接的ON部分