Question

所以我有三张桌子。 CUSTOMER（ CustomerID ，LastName，FirstName），PURCHASE（ PurchaseID ，ItemName）和TRANSACTION（ CustomerID ， PurchaseID ，日期）。

我遇到的问题是我需要获得专门购买“Paint”和“Books”两个项目的客户的全名，但是当我运行我的代码时，没有任何问题出现。这就是我所拥有的：

SELECT CUSTOMER.FirstName, CUSTOMER.LastName
FROM CUSTOMER, PURCHASE
WHERE PURCHASE.Item = 'Paint' AND PURCHASE.Item = 'Books'
GROUP BY CUSTOMER.LastName, CUSTOMER.FirstName;

请帮助，我真的很陌生，真的很想帮忙。

Answer 1

此类问题称为Relational Division。

SELECT  CUSTOMER.FirstName, CUSTOMER.LastName
FROM    CUSTOMER    
        INNER JOIN TRANSACTION
            ON CUSTOMER.CustomerID = TRANSACTION.CustomerID
        INNER JOIN PURCHASE
            ON TRANSACTION.PurchaseID = PURCHASE.PurchaseID
WHERE   PURCHASE.Item IN ('Paint', 'Books')  -- list all items here
GROUP   BY CUSTOMER.LastName, CUSTOMER.FirstName
HAVING  COUNT(DISTINCT PURCHASE.Item) = 2 -- the total number of items searched

SQL of Relational Division

如果在每笔交易中对每个UNIQUE强制执行ItemName约束，您可以使用*

SELECT  CUSTOMER.FirstName, CUSTOMER.LastName
FROM    CUSTOMER    
        INNER JOIN TRANSACTION
            ON CUSTOMER.CustomerID = TRANSACTION.CustomerID
        INNER JOIN PURCHASE
            ON TRANSACTION.PurchaseID = PURCHASE.PurchaseID
WHERE   PURCHASE.Item IN ('Paint', 'Books')
GROUP   BY CUSTOMER.LastName, CUSTOMER.FirstName
HAVING  COUNT(*) = 2

Answer 2

没有连接..

SELECT DISTINCT CUSTOMER.FirstName, CUSTOMER.LastName
FROM CUSTOMER A 
JOIN TRANSACTION B
ON A.CUSTOMERID=B.CUSTOMERID
JOIN PURCHASE C
ON B.PURCHASEID=C.PURCHASEID AND C.ITEM='Paint'
JOIN PURCHASE D 
ON B.PURCHASEID=D.PURCHASEID AND D.C.Item = 'Books'

Answer 3

您需要JOIN个表格。尝试

SELECT CUSTOMER.FirstName, CUSTOMER.LastName
FROM   CUSTOMER 
       INNER JOIN TRANSACTION ON TRANSACTION.CustomerID=CUSTOMER.CustomerID 
       INNER JOIN PURCHASE ON PURCHASE.PurchaseID=TRANSACTION.PurchaseID
WHERE PURCHASE.Item = 'Paint' OR PURCHASE.Item = 'Books'
GROUP BY CUSTOMER.LastName, CUSTOMER.FirstName
HAVING COUNT(DISTINCT PURCHASE.Item) >= 2;

Answer 4

SELECT CUSTOMER.FirstName, CUSTOMER.LastName
FROM CUSTOMER C, PURCHASE P, TRANSACTION T
WHERE
C.CUSTOMERID = T.CUSTOMERID AND T.PurchaseID = P.PurchaseID
AND P.Item IN ('Paint','Books')

这是伪代码。亲自尝试一下。

SQL检索基于多个表的名称

4 个答案: