mysql 字段初始化

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100),
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    status ENUM('active', 'inactive') DEFAULT 'active',
    counter INT DEFAULT 0
);

-- 错误的插入语句
INSERT INTO users (username, email) VALUES ('JohnDoe', 'john@example.com');

-- 正确的插入语句
INSERT INTO users (username, email) VALUES ('JohnDoe', 'john@example.com');

CREATE TABLE orders (
    id INT AUTO_INCREMENT PRIMARY KEY,
    order_date DATE DEFAULT CURRENT_DATE,
    total_amount DECIMAL(10, 2) DEFAULT 0.00
);

ALTER TABLE users
ALTER COLUMN created_at SET DEFAULT CURRENT_TIMESTAMP;