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sql - 计算客户购买商品的平均价格

问题描述

我有三个表：客户、订单和订单项。它们的设置如下：

CREATE TABLE cust_account(
cust_id DECIMAL(10) NOT NULL,
first VARCHAR(30),
last VARCHAR(30),
address VARCHAR(50),
PRIMARY KEY (cust_id));

CREATE TABLE orders(
order_num DECIMAL(10) NOT NULL,
cust_id DECIMAL(10) NOT NULL,
order_date DATE,
PRIMARY KEY (order_num));

CREATE TABLE lines(
order_num DECIMAL(10) NOT NULL,
line_id DECIMAL(10) NOT NULL,
item_num DECIMAL(10) NOT NULL,
price DECIMAL(10),
PRIMARY KEY (order_id, line_id),
FOREIGN KEY (item_id) REFERENCES products);

使用 Oracle，我需要编写一个查询，显示购买超过 5 次或更多的客户的平均商品价格。这是我一直在使用的：

SELECT DISTINCT cust_account.cust_id,cust_account.first, cust_account.last, lines.AVG(price) AS average_price
FROM cust_account
 JOIN orders
 ON cust_account.cust_id = orders.cust_id
 JOIN lines
 ON lines.order_num = orders.order_num
 WHERE lines.item_num IN (SELECT lines.item_num
    FROM lines
    JOIN orders
    ON lines.order_num = orders.order_num
        GROUP BY lines.order_num
        HAVING COUNT(DISTINCT orders.cust_id) >= 5
    );

标签： sqloraclejoinsubquerywhere

解决方案

  1. ...INNER JOIN你所有的桌子在一起
  2. ...GROUP BY客户并计算每个客户行的平均价格
  3. ...使用一个HAVING子句将结果限制为购买 5 次或更多的组

由于这闻起来像家庭作业，所以我会在长时间的停顿后发布完整的答案......

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SELECT   ca.first, ca.last, avg(l.price) avg_price
FROM     cust_account ca
INNER JOIN orders o ON o.cust_id = ca.cust_id
INNER JOIN lines l ON l.order_num = o.order_number
GROUP BY ca.first, ca.last
HAVING COUNT(distinct l.line_id) >=5
-- OR, maybe your requirement is ...
-- HAVING COUNT(distinct o.order_num) >= 5
-- ... the question was a bit unclear on this point

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