mysql不允许重复值

-- 创建表并设置单列唯一约束
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) UNIQUE,
    email VARCHAR(100) UNIQUE
);

-- 创建表并设置复合唯一约束
CREATE TABLE orders (
    order_id INT AUTO_INCREMENT PRIMARY KEY,
    customer_id INT,
    order_date DATE,
    UNIQUE (customer_id, order_date)
);

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)", ('user1', 'user1@example.com'))
    conn.commit()
except mysql.connector.IntegrityError as err:
    print(f"Error: {err}")
finally:
    cursor.close()
    conn.close()

-- 更新唯一约束列的值
UPDATE users SET email = 'new_email@example.com' WHERE username = 'user1';