mysql新增一条记录

-- 单条记录插入
INSERT INTO users (username, email, password) VALUES ('user1', 'user1@example.com', 'password1');

-- 多条记录插入
INSERT INTO users (username, email, password) VALUES 
('user2', 'user2@example.com', 'password2'),
('user3', 'user3@example.com', 'password3');

-- 从其他表插入
INSERT INTO user_profiles (user_id, first_name, last_name)
SELECT id, first_name, last_name FROM users WHERE status = 'active';

-- 使用INSERT IGNORE
INSERT IGNORE INTO users (username, email, password) VALUES ('user1', 'user1@example.com', 'password1');

-- 使用ON DUPLICATE KEY UPDATE
INSERT INTO users (username, email, password) 
VALUES ('user1', 'user1@example.com', 'password1')
ON DUPLICATE KEY UPDATE password = 'new_password';

-- 修改列的定义
ALTER TABLE users MODIFY COLUMN email VARCHAR(255);