SQL Server查詢：使用JOIN包含NULL值

Question

我需要以下SQL Server查詢幫助，其中列a.TAProfileID和c.CountryCode在數據庫中具有「NULL」值。

我想我的JOIN語句返回它們存在的「NULL」值。

SELECT 
a.ReservationStayID AS 'Reservation Id', 
a.PMSConfirmationNumber as 'PMS No', 
a.CreatedOn AS 'Date Created', 
a.ArrivalDate AS 'Date of Arrival', 
a.DepartureDate AS 'Date of Departure', 
a.TAProfileID AS 'TA Id', 
a.StatusCode AS 'Status', 
b.PropertyCode AS 'Hotel', 
c.Name AS 'Travel Agency', 
c.CountryCode AS 'Market Code', 
d.CountryName AS 'Mkt' 

FROM ReservationStay a 

inner JOIN GuestStaySummary b ON a.ReservationStayID = b.ReservationStayID 
inner JOIN TravelAgency c ON a.TAProfileID = c.TravelAgencyID 
inner JOIN Market d ON c.CountryCode = d.CountryCode 

Answer 1

爲了回報或產生NULL值，你將不得不使用LEFT JOIN秒。

所以，你的查詢應該是這樣的：

SELECT 
    a.ReservationStayID AS 'Reservation Id' 
    ,a.PMSConfirmationNumber AS 'PMS No' 
    ,a.CreatedOn AS 'Date Created' 
    ,a.ArrivalDate AS 'Date of Arrival' 
    ,a.DepartureDate AS 'Date of Departure' 
    ,a.TAProfileID AS 'TA Id' 
    ,a.StatusCode AS 'Status' 
    ,b.PropertyCode AS 'Hotel' 
    ,c.NAME AS 'Travel Agency' 
    ,c.CountryCode AS 'Market Code' 
    ,d.CountryName AS 'Mkt' 
FROM ReservationStay a 
    INNER JOIN GuestStaySummary b ON a.ReservationStayID = b.ReservationStayID 
    LEFT JOIN TravelAgency c ON a.TAProfileID = c.TravelAgencyID 
    LEFT JOIN Market d ON c.CountryCode = d.CountryCode