如何在子查询 SQL 服务器中使用 Left Join？

Question

我正在尝试在 SQL 服务器的子查询中使用左连接。我的查询看起来不错，但出现语法错误。

这是我的查询：

(
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

这是我遇到的错误：

这是我的 table 结构：

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

如@Chris 所述，查询有点不完整。我猜你正在尝试做这样的事情：

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 */

这个查询对我有用。如果必须更改某些内容，请评论此答案。

如何在子查询 SQL 服务器中使用 Left Join？

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