mysql 查询unique

-- 创建表并添加单列唯一约束
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    email VARCHAR(100) NOT NULL UNIQUE
);

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

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

import mysql.connector

try:
    conn = mysql.connector.connect(user='your_user', password='your_password', host='your_host', database='your_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()