SQL Query与其他表JOINED时拉取NULL值

Question

您好，感谢您的阅读。我似乎在查询中从字段中提取日期时遇到问题。 Query中的所有其他字段都正确拉动，并且不会引发错误。但是，所有Document.ServiceDTTM列都显示NULL。 Document表中没有NULL值，所以我不确定为什么会显示它。我在某处使用了错误的JOIN类型吗？

    DECLARE @StartDate datetime
    DECLARE @EndDate datetime

    SET @StartDate = '2015-08-01'
    SET @EndDate = '2015-09-01'
    USE Works

    SELECT Patient_Iorg.organizationMRN AS MRN, IDX_User.AUsername AS TWUser, Document.ServiceDTTM, DocumentEvent.eventDTTM, Document_Type_de.EntryName AS NoteName FROM Document (nolock)
        JOIN DocumentEvent ON Document.documentid = DocumentEvent.documentid
        JOIN Document_Type_de ON Document.documenttypede = Document_Type_de.ID
        JOIN IDX_User ON DocumentEvent.userid = IDX_User.ID
        JOIN Person ON Document.PatientID = Person.ID
        LEFT JOIN Patient_Iorg ON Person.id = Patient_Iorg.PersonID and Patient_Iorg.InternalOrganization = 3
    WHERE 
        DocumentEvent.documenteventde IN (18)
    AND
        DocumentEvent.eventDTTM >= @StartDate 
    AND 
        DocumentEvent.eventDTTM <= @EndDate 
    AND 
        Document.Status LIKE 'Final%' 
    AND 
        Document.DocumentTypeDE IN (158) 

ORDER BY 
    eventDTTM

以下信息：

XXXXXX  adoctor     NULL    8/1/2015    Note
XXXXXX  adoctor     NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note
XXXXXX  aprovider       NULL    8/1/2015    Note