MySQL创建表并设置主键与外键 - 详细教程

创建表并设置主键：

CREATE TABLE users (
  id INT PRIMARY KEY,
  username VARCHAR(50),
  password VARCHAR(50)
);

创建表并设置外键：

CREATE TABLE orders (
  id INT PRIMARY KEY,
  user_id INT,
  order_date DATE,
  FOREIGN KEY (user_id) REFERENCES users(id)
);