mysql数据库唯一非空

-- 创建表时添加唯一非空约束
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    email VARCHAR(100) NOT NULL UNIQUE
);

-- 添加唯一非空约束
ALTER TABLE users ADD CONSTRAINT unique_email UNIQUE (email);

-- 插入数据
INSERT INTO users (username, email) VALUES ('john_doe', 'john@example.com');

-- 尝试插入重复数据（会报错）
INSERT INTO users (username, email) VALUES ('john_doe', 'john@example.com');

import mysql.connector

try:
    conn = mysql.connector.connect(user='user', password='password', host='host', database='database')
    cursor = conn.cursor()
    cursor.execute("INSERT INTO users (username, email) VALUES (%s, %s)", ('john_doe', 'john@example.com'))
    conn.commit()
except mysql.connector.IntegrityError as err:
    print(f"Error: {err}")
finally:
    cursor.close()
    conn.close()