Question

我有这样的表格：

表：因素

FactorID   SellerID   ContractorID
---------------------------------
1            -1          2
2             1         -1
3            -1          1
4             2         -1

表：卖家

SellerID   SellerName
---------------------
1            SellerA      
2            SellerB      
3            SellerC      
4            SellerD

表承包商：

ContractorID   ContractorName
-------------------------------
1                    W      
2                    X      
3                    Y      
4                    Z

我希望查询返回如下：

FactorID   SellerID   ContractorID   ContractorName     SellerName
------------------------------------------------------------------
1            -1          2                  X                NULL
2             1         -1                  NULL             SellerA
3            -1          1                  W                NULL   
4             2         -1                  NULL             SellerB

这是我的查询，但没有正常工作：

SELECT  Factos.* ,
        Seller.sellerName AS sellerName ,
        Contractor.Contractor AS contractorName
FROM    Fctors ,
        Seller ,
        Contractor
WHERE   Seller.SellerID = CASE WHEN Factors.ContrarID = -1 THEN Factors.SellerID
                               ELSE ''
                          END
        AND Contractor.ContractorID = CASE WHEN Factors.SellerID = -1 THEN Factors.ContractorID
                                           ELSE ''
                                      END

Answer 1

一个简单的JOIN语句应该提供所需的结果而不需要任何CASE语句

SELECT f.*, s.sellerName as sellerName, c.Contractor as contractorName
  FROM Factors f
  LEFT OUTER JOIN Sellers s ON(f.SellerId=s.SellerId)
  LEFT OUTER JOIN Contractors c ON(f.ContractorId=c.ContractorId)

Answer 2

请尝试：

SELECT a.*, b.SellerName, c.ContractorName
FROM
Factors A LEFT JOIN Sellers b on a.SellerID=b.SellerID
    LEFT JOIN Contractors c on a.ContractorID=c.ContractorID

Answer 3

我认为您只需使用查询即可获得该结果，请查看以下查询

SELECT F.FactorID, S.SellerID, C.ContractorID, C.ContractorName, S.SellerName FROM FACTORS F LEFT JOIN SELLERS S ON F.SellerID = S.SellerID
          LEFT JOIN CONTRACTORS C ON F.ContractorID = C.ContractorID

Answer 4

SELECT Factors.FactorID,Sellers.SellerID AS SellerID ,
Contractors.ContractorID AS ContractorID,
Contractors.ContractorName AS ContractorName,
Sellers.SellerName AS SellerName

FROM Factors LEFT JOIN Sellers ON Factors.FactorID=Sellers.SellerID
LEFT JOIN Contractors ON Factors.FactorID=Contractors.ContractorID

Answer 5

Left Outer join就是您所需要的一切

select f.FactorID, f.SellerID, f.ContractorID, c.ContractorName, s.SellerName
from Factors f left outer join Sellers s on f.SellerID = s.SellerID
    left outer join Contractors c on f.ContractorID = c.ContractorID

Answer 6

无需使用CASE。 LEFT OUTER JOIN应该足够了。应该这样做：

  SELECT f.FactorID,
         f.SellerID,
         f.ContractorID,
         c.ContractorName,
         s.SellerName
    FROM Factors f
         LEFT OUTER JOIN Sellers s 
                         ON f.SellerID = s.SellerID
         LEFT OUTER JOIN Contractor c
                         ON f.SellerID = c.SellerID
ORDER BY f.FactorID ASC;

条件选择的SQL查询

6 个答案: