基于等保的教材征订信息管理系统与排行榜

CREATE TABLE books (

book_id INT PRIMARY KEY,

title VARCHAR(255),

author VARCHAR(255),

price DECIMAL(10,2)

综合服务门户

);

CREATE TABLE orders (

order_id INT PRIMARY KEY,

user_id INT,

book_id INT,

FOREIGN KEY (book_id) REFERENCES books(book_id)

);

CREATE TABLE rankings (

book_id INT PRIMARY KEY,

rank INT,

FOREIGN KEY (book_id) REFERENCES books(book_id)

);

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UPDATE rankings r

JOIN (

SELECT book_id, COUNT(*) AS order_count

FROM orders

GROUP BY book_id

) o ON r.book_id = o.book_id

SET r.rank = o.order_count;

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