如何在子查詢 SQL Server 中使用 Left Join？

Question

我正在嘗試在 SQL Server 的子查詢中使用左連接。 我的查詢對我來說很好，但它給出了語法錯誤。

這是我的查詢：

(
SELECT 
    FK_OrderNo AS LHNo, VendorName AS LHVendor
FROM 
    tbl_ShipmentAPAR 
LEFT JOIN
    tbl_vendors ON FK_VendorID = VendorID
WHERE
    FK_ServiceID = 'LH'
) LHBase ON PK_OrderNo = LHNo 
LEFT JOIN 
    (SELECT
         FK_OrderNo AS DANo,
         VendorName AS DAVendor
     FROM 
         tbl_ShipmentAPAR 
     LEFT JOIN 
         tbl_vendors ON FK_VendorId = VendorId
     WHERE 
         FK_ServiceId = 'DA') DABase ON PK_OrderNo = DANo

這是我得到的錯誤：

這是我的表結構：

CREATE TABLE tbl_ShipmentAPAR 
(
     VendorID int PRIMARY KEY,
     VendorName varchar(200), 
     FK_OrderNo int 
)

CREATE TABLE tbl_vendors
(
     FK_VendorID int, 
     FOREIGN KEY (FK_VendorID) REFERENCES tbl_ShipmentAPAR(VendorID), 
     FK_ServiceID varchar(200)
)

INSERT INTO tbl_ShipmentAPAR VALUES (1, 'John',123)
INSERT INTO tbl_vendors VALUES (1,'LH')

Answer 1

正如@Chris 提到的，查詢有點不完整。 我猜你正在嘗試做這樣的事情：

SELECT * FROM    /*--> Added new */
(
SELECT 
    FK_OrderNo AS LHNo, VendorName AS LHVendor
FROM 
    tbl_ShipmentAPAR
LEFT JOIN
    tbl_vendors ON FK_VendorID = VendorID
WHERE
    FK_ServiceID = 'LH'
) LHBase
LEFT JOIN 
    (SELECT
         FK_OrderNo AS DANo,
         VendorName AS DAVendor
     FROM 
         tbl_ShipmentAPAR 
     LEFT JOIN 
         tbl_vendors ON FK_VendorId = VendorId
     WHERE 
         FK_ServiceId = 'DA') DABase ON LHBase.LHNo = DABase.DANo /* -->Modified PKOrder no to LHNo because PKOrder no doesn't exist in either of the sub-queries */

這個查詢對我有用。 如果必須更改某些內容，請對此答案發表評論。