MySQL如何创建带有子查询的 View ？

Question

我想创建一个名为 OrderSummary 的 View ，其中包含 CUSTOMER.FirstName、CUSTOMER.LastName、INVOICE.InvoiceDate 和发票总计(通过确定 INVOICE_ITEM.Quantity 的总和乘以 SERVICE.ServicePrice 来计算)。我想使用子查询来确定发票总额。感谢您的帮助。

CREATE VIEW OrderSummaryView AS
    SELECT c.FirstName, c.LastName, i.InvoiceDate
FROM CUSTOMER c, INVOICE i, SERVICE s  
WHERE c.CustomerID = i.InvoiceID  
AND c.CustomerID = s.ServiceID; 
SELECT sum(UnitPrice) * Quantity AS InvoiceTotal
FROM        SERVICE, INVOICE_ITEM
WHERE       SERVICE.ServiceID = invoice_item.InvoiceID

Answer 1

您应该首先处理 select 语句以包含特定于连接的语法

SELECT c.FirstName, c.LastName, i.InvoiceDate
FROM CUSTOMER c
JOIN INVOICE i ON c.CustomerID = i.InvoiceID 
JOIN INVOICE_ITEM ii ON ii.InvoiceID = i.InvoiceID 
JOIN SERVICE s ON ii.ServiceID = s.ServiceID;

然后我们可以添加您的其他子查询

SELECT c.FirstName, c.LastName, i.InvoiceDate, t.InvoiceTotal
FROM CUSTOMER c
JOIN INVOICE i ON c.CustomerID = i.InvoiceID 
JOIN INVOICE_ITEM ii ON ii.InvoiceID = i.InvoiceID 
JOIN SERVICE s ON ii.ServiceID = s.ServiceID
JOIN
(   SELECT SUM(UnitPrice) * Quantity AS InvoiceTotal, i.InvoiceID
    FROM SERVICE s
    JOIN INVOICE_ITEM i ON i.InvoiceID = s.ServiceID
    GROUP BY i.InvoiceID
) as t ON t.InvoiceID = i.InvoiceID;

有一点看起来有点可疑，那就是 customerid = Invoiceid = serviceid 您确定所有这些都是正确的 pk -> fk 关系吗？

要创建带有 subview 的 View ，您必须分两步完成

CREATE VIEW cust_inv_serv AS 
    SELECT c.FirstName, c.LastName, i.InvoiceDate, i.InvoiceID
    FROM CUSTOMER c
    JOIN INVOICE i ON c.CustomerID = i.InvoiceID 
    JOIN INVOICE_ITEM ii ON ii.InvoiceID = i.InvoiceID 
    JOIN SERVICE s ON ii.ServiceID = s.ServiceID;

CREATE VIEW OrderSummaryView AS 
    SELECT v.FirstName, v.LastName, v.InvoiceDate, v.InvoiceID, SUM(UnitPrice) * Quantity AS InvoiceTotal
    FROM SERVICE s
    JOIN INVOICE_ITEM i ON i.InvoiceID = s.ServiceID
    JOIN cust_inv_serv v ON v.InvoiceID = i.InvoiceID
    GROUP BY i.InvoiceID;