mysql数据库建表脚本

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    email VARCHAR(100) NOT NULL UNIQUE,
    password VARCHAR(255) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    email VARCHAR(100) NOT NULL UNIQUE,
    password VARCHAR(255) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

ALTER TABLE users MODIFY COLUMN email VARCHAR(200);

INSERT INTO users (username, email, password)
VALUES ('john_doe', 'john@example.com', 'password123')
ON DUPLICATE KEY UPDATE username=VALUES(username), email=VALUES(email), password=VALUES(password);