mysql数据库主键跟外键

-- 创建自增主键
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255) NOT NULL
);

-- 插入数据
INSERT INTO users (name) VALUES ('Alice');
INSERT INTO users (name) VALUES ('Bob');

-- 创建分类表
CREATE TABLE categories (
    id INT PRIMARY KEY,
    name VARCHAR(255) NOT NULL
);

-- 创建产品表
CREATE TABLE products (
    id INT PRIMARY KEY,
    name VARCHAR(255) NOT NULL,
    category_id INT,
    FOREIGN KEY (category_id) REFERENCES categories(id)
);

-- 插入分类数据
INSERT INTO categories (id, name) VALUES (1, 'Electronics');
INSERT INTO categories (id, name) VALUES (2, 'Clothing');

-- 插入产品数据
INSERT INTO products (id, name, category_id) VALUES (1, 'Laptop', 1);
INSERT INTO products (id, name, category_id) VALUES (2, 'T-Shirt', 2);