左连接上的我的SQL未知列

Question

我被困在左连接上，看不出我做错了什么。我在'on子句'中的'_JobTable.JobTypeID'上得到一个未知列，但无法解决。

任何人都可以指出我只是忽略了什么，并且为了以后会打到自己的脑袋？

SELECT
_RefTable.RefID,
_JobTable.JobID,
_Client.ClientName,
_Type.Description,
_Job.JobDetails,
_RefTable.SiteID,
_RefTable.SiteName,
_RefTable.SiteAddressState,
_RefTable.SiteAddressSuburb

from _RefTable 

LEFT JOIN(
            SELECT
            _JobTable.JobID,
            _JobTable.JobTypeID,
            _JobTypeTable.Description
            FROM  _JobTable, _JobTypeTable WHERE _JobTable.JobTypeID = _JobTypeTable.JobTypeID
            ) as _Type on _JobTable.JobTypeID = _Type.JobTypeID

LEFT JOIN(
            SELECT
            _RefTable.RefID,
            _ClientTable.ClientName
            FROM _RefTable, _ClientTable WHERE _RefTable.ClientID = _ClientTable.ClientID
            ) as _Client on _RefTable.RefID = _Client.RefID

LEFT JOIN(
            SELECT
            _RefTable.RefID,
            _JobTable.JobID,
            _JobTable.JobDetails
            FROM  _RefTable, _JobTable  WHERE _RefTable.RefID = _JobTable.RefID 
            ) as _Job on _RefTable.RefID = _Job.RefID