更改表格以更改时间范围[WHERE / ALTER]

Question

编辑：当前正在运行SQuirreL SQL v.3.8.0。

我创建并保存了一个表，该表使用WHERE语句在特定时间范围内提取客户数据。我如何更新时间框架？我尝试使用ALTER TABLE函数来更改WHERE语句，但收到错误消息。

原始表

SELECT Customer,
AVG(CAST(ItemPrice AS FLOAT)) AS item_price, 
COUNT(DISTINCT(ReceiptIDDesc)) AS number_of_orders, 
SUM(CAST(ItemPrice AS FLOAT)) AS total_spend
INTO Customer_data_A
FROM Tacos 
Where (CAST(PurchaseDate AS DateTime) >= '01/01/2017 12:00') AND (CAST(PurchaseDate AS DateTime) <= '12/01/2017 12:00')
GROUP BY Customer

改变声明

ALTER TABLE Customer_data_A ALTER COLUMN * WHERE (CAST(PurchaseDate AS DateTime) >= '01/01/2017 12:00') AND (CAST(PurchaseDate AS DateTime) <= '11/01/2017 12:00')

这给了我以下错误消息：

错误：'*'附近的语法不正确。

SQLState：S0001

ErrorCode：102

Answer 1

在大多数SQL方言中，您使用的查询基本上是“执行此查询并将结果存储到新表中”。新表与用于获取数据的查询之间没有任何关系。

你可能真正想要使用的是视图（总是显示给出的查询的当前数据 - 想想“命名查询”）或物化视图（实际上将数据存储在表中，但是用户可以从新的结果中触发数据的刷新查询）。

Answer 2

听起来您正在寻找TRUNCATE现有数据并加载（INSERT INTO）现有的表结构？

ALTER TABLE + ALTER COLUMN将更多地用于更改数据类型或添加约束（即将INT列更改为NUMERIC或添加外键引用）。

TRUNCATE TABLE Customer_data_A;

INSERT INTO Customer_data_A
(Customer, ItemPrice, Number_Of_Orders, Total_Spend)
SELECT Customer
      ,AVG(CAST(ItemPrice AS FLOAT)) AS item_price
      ,COUNT(DISTINCT(ReceiptIDDesc)) AS number_of_orders
      ,SUM(CAST(ItemPrice AS FLOAT)) AS total_spend
FROM Tacos 
WHERE (CAST(PurchaseDate AS DateTime) >= '01/01/2017 12:00') AND (CAST(PurchaseDate AS DateTime) <= '11/01/2017 12:00')
GROUP BY Customer;