select periodName , DeptName , convert(varchar(20),AppointTime,23) AppointTime, app.* from appointList app  
inner join periodList per on app.periodID=per.periodID
inner join DeptList dl on app.DeptID=dl.ID

select periodName , DeptName , convert(varchar(20),AppointTime,23) AppointTime, app.* from appointList app  
from appointList app , periodList per , DeptList dl
where app.periodID=per.periodID and app.DeptID=dl.ID

------解决方案--------------------
就是你之前的那个表名写在一起，然后用where加条件就可以了，不用on来连接

------解决方案--------------------
探讨

SQL code
select periodName , DeptName , convert(varchar(20),AppointTime,23) AppointTime, app.* from appointList app  
inner join periodList per on app.periodID=per.periodID
inner join DeptList dl o……