如何在插入前检查数据库的重复项？

import pymysql

def check_duplicate_data(data):
    # 连接数据库
    conn = pymysql.connect(host='localhost', user='root', password='password', db='mydb')
    cursor = conn.cursor()

    # 查询数据库，检查重复项
    query = "SELECT * FROM mytable WHERE unique_field = %s"
    cursor.execute(query, (data['unique_field'],))
    result = cursor.fetchone()

    if result:
        # 存在重复项
        print("Duplicate data found!")
        # 执行其他操作，如更新现有记录

    else:
        # 不存在重复项，执行插入操作
        insert_query = "INSERT INTO mytable (unique_field, other_field) VALUES (%s, %s)"
        cursor.execute(insert_query, (data['unique_field'], data['other_field']))
        conn.commit()
        print("Data inserted successfully!")

    # 关闭数据库连接
    cursor.close()
    conn.close()

# 要插入的数据
data = {
    'unique_field': '12345',
    'other_field': 'Some data'
}

# 调用函数进行检查和插入操作
check_duplicate_data(data)