函数返回字符串在多列中的频率百分比

import mysql.connector

def calculate_percentage(string, columns):
    # 连接到数据库
    cnx = mysql.connector.connect(user='username', password='password',
                                  host='localhost', database='database_name')
    cursor = cnx.cursor()

    # 执行查询语句
    query = "SELECT {} FROM table_name".format(','.join(columns))
    cursor.execute(query)

    total_count = 0
    string_count = 0

    # 遍历结果集
    for row in cursor:
        for value in row:
            # 统计总次数和字符串出现的次数
            total_count += 1
            if value == string:
                string_count += 1

    # 计算百分比
    percentage = (string_count / total_count) * 100

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

    # 返回结果
    return "{:.2f}%".format(percentage)

# 示例调用
string = "example"
columns = ["column1", "column2", "column3"]
result = calculate_percentage(string, columns)
print(result)