MySQL数据库设计实战之如何从需求到建表(完整流程)

✅ 用户（User）
✅ 订单（Order）
✅ 订单明细（Order Item）

id, name, email, city

订单ID → 用户ID → 用户名、城市
       直接依赖   传递依赖（不应该存）

id, user_id, total_amount, status, created_at

订单明细ID → 订单ID → 订单总金额、用户ID → 用户名
           直接依赖   传递依赖（不应该存）

id, order_id, product_name, quantity, price

graph LR
    A[order_items表] -->|order_id| B[orders表]
    B -->|user_id| C[users表]
    A -->|只存：商品信息| A
    B -->|只存：订单信息| B
    C -->|只存：用户信息| C

CREATE DATABASE IF NOT EXISTS sql_optimization_test;
USE sql_optimization_test;

CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL,
    email VARCHAR(100),
    city VARCHAR(50),
    INDEX idx_city (city)  -- 按城市查询的索引
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

CREATE TABLE orders (
    id INT PRIMARY KEY AUTO_INCREMENT,
    user_id INT NOT NULL,
    total_amount DECIMAL(10,2) NOT NULL DEFAULT 0.00,
    status VARCHAR(20) NOT NULL DEFAULT 'pending',
    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_user_id (user_id),       -- JOIN时用
    INDEX idx_status (status),         -- 按状态查询
    INDEX idx_created_at (created_at), -- 按时间查询
    FOREIGN KEY (user_id) REFERENCES users(id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

CREATE TABLE order_items (
    id INT PRIMARY KEY AUTO_INCREMENT,
    order_id INT NOT NULL,
    product_name VARCHAR(100) NOT NULL,
    quantity INT NOT NULL DEFAULT 1,
    price DECIMAL(10,2) NOT NULL,
    INDEX idx_order_id (order_id),          -- JOIN时用
    INDEX idx_product_name (product_name),  -- 按商品查询
    FOREIGN KEY (order_id) REFERENCES orders(id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

SELECT u.name, o.id, o.total_amount, o.status
FROM users u
JOIN orders o ON u.id = o.user_id
WHERE u.city = '深圳';

SELECT DISTINCT u.id, u.name, u.email
FROM users u
JOIN orders o ON u.id = o.user_id
JOIN order_items oi ON o.id = oi.order_id
WHERE oi.product_name LIKE '%iPhone%';

SELECT u.id, u.name, SUM(o.total_amount) AS total
FROM users u
LEFT JOIN orders o ON u.id = o.user_id
GROUP BY u.id, u.name
ORDER BY total DESC;

-- 生成1000个用户
DELIMITER $$
CREATE PROCEDURE generate_users()
BEGIN
    DECLARE i INT DEFAULT 1;
    WHILE i <= 1000 DO
        INSERT INTO users (name, email, city) VALUES (
            CONCAT('用户', i),
            CONCAT('user', i, '@example.com'),
            ELT(FLOOR(1 + RAND() * 5), '深圳', '北京', '上海', '广州', '杭州')
        );
        SET i = i + 1;
    END WHILE;
END$$
DELIMITER ;
CALL generate_users();

需求分析 → 找主体 → 画E-R图 → 确定字段 → 检查范式 → 建表 → 验证

FOREIGN KEY (user_id) REFERENCES users(id)