mysql 创建表设置默认值

CREATE TABLE table_name (
    column1 datatype DEFAULT default_value,
    column2 datatype,
    ...
);

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    status VARCHAR(10) DEFAULT 'active'
);

-- 错误示例：类型不匹配
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    created_at TIMESTAMP DEFAULT 'default_value' -- 错误：'default_value' 不是 TIMESTAMP 类型
);

-- 正确示例
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP -- 正确：CURRENT_TIMESTAMP 是 TIMESTAMP 类型
);