mysql手动添加数据

-- 基本插入语句
INSERT INTO users (username, email, age) VALUES ('john_doe', 'john@example.com', 30);

-- 插入数据并忽略重复
INSERT IGNORE INTO users (username, email, age) VALUES ('jane_doe', 'jane@example.com', 25);

-- 插入数据，如果存在则更新
INSERT INTO users (username, email, age) 
VALUES ('john_doe', 'john_new@example.com', 31) 
ON DUPLICATE KEY UPDATE email = VALUES(email), age = VALUES(age);

-- 使用INSERT IGNORE
INSERT IGNORE INTO users (username, email, age) VALUES ('john_doe', 'john@example.com', 30);

-- 使用INSERT ... ON DUPLICATE KEY UPDATE
INSERT INTO users (username, email, age) 
VALUES ('john_doe', 'john@example.com', 30) 
ON DUPLICATE KEY UPDATE age = VALUES(age);

-- 修改表结构，增加字段长度
ALTER TABLE users MODIFY COLUMN email VARCHAR(255);