Question

我有3个sql表：首先我用关键PID存储产品。第二，我用密钥RID保存发票。第三个表用于描述在此发票中购买的每种产品的数量。我需要一个关于这两个问题的帮助，作为一个很少使用sql的人，这有点难。

1）过去3个月内购买的产品最多的是什么。

2）将这3种产品的价格提高5％的查询是什么？

DB：

CREATE TABLE Products(
    pid INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    name VARCHAR(30) NOT NULL,
    type VARCHAR(8) NOT NULL,
    price DOUBLE NOT NULL,
    stock INTEGER NOT NULL);

CREATE TABLE Invoices(
    rid INTEGER GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    invoicedate TIMESTAMP NOT NULL);

CREATE TABLE Orders(
    rid INTEGER,
    pid INTEGER,
    quantity INTEGER NOT NULL,
    FOREIGN KEY (pid) REFERENCES Products(pid) ON DELETE CASCADE,
    FOREIGN KEY (rid) REFERENCES Invoices(rid) ON DELETE CASCADE);

Answer 1

提高价格

    update product set price=price*. 05 where pid in( give your pid seperated by comma)

Answer 2

对于第一个查询，您没有指定要获得的产品数量，因此这里有一个查询，用于检索已购买的所有产品，按数量最多订购到更少：

SELECT P.name, P.type, SUM(O.quantity) Quant
FROM Orders AS O
INNER JOIN Products AS P
ON O.pid = P.pid
GROUP BY P.name, P.type
ORDER BY Quant DESC

对于UPDATE，这是一种使用SQL Server的方法：

UPDATE Products
SET price = price * 1.05
WHERE pid IN (  SELECT DISTINCT P.pid 
                FROM Orders AS O
                INNER JOIN Products AS P
                ON O.pid = P.pid
                GROUP BY P.pid
                ORDER BY SUM(O.Quantity) DESC)

如何使用这3个表获得所需的查询

2 个答案: