mysql字段设置成不能重复

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

import mysql.connector

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