Question

我想使用以下代码创建视图：

SELECT t1.FirstName, t1.LastName, t2.Sum FROM Customer as t1,(SELECT CustomerID,Sum(Total) as Sum  FROM Invoice GROUP BY(CustomerID)) as t2 WHERE t1.CustomerID=t2.CustomerID

对我有意义的方法是做

Create VIEW t2 as SELECT CustomerID,Sum(Total) as Sum  FROM Invoice GROUP BY(CustomerID)

Create VIEW CustomerInvoices as SELECT t1.FirstName, t1.LastName, t2.Sum FROM Customer as t1, t2  WHERE t1.CustomerID=t2.CustomerID

但是这给了我一个语法错误，所以我不确定如何在主视图中调用第一个视图

Answer 1

正如您所注意到的，MySQL中不允许使用此语法（尽管在其他数据库中允许使用此语法）：

SELECT t1.FirstName, t1.LastName, t2.Sum
FROM Customer as t1 JOIN
     (SELECT CustomerID,Sum(Total) as Sum  FROM Invoice GROUP BY(CustomerID)
     ) t2 
     ON t1.CustomerID = t2.CustomerID;

您可以将其改为：

SELECT c.FirstName, c.LastName, sum(total) as sum
FROM Customer c JOIN
     Invoice i
     ON c.CustomerID = i.CustomerId
GROUP BY c.FirstName, c.LastName;

这将在视图中有效。

使用子查询创建视图的正确语法？

1 个答案: