Tkinter登录页匹配SQL数据库记录时遇'Unread result found'错误求助

我正在做一个SQL-Python连接器的学习项目，做了一个简单的Tkinter登录页用来输入用户名和密码，同时搭建了存储账号密码的数据库。目标是通过SQL-Python连接器把登录页的输入和数据库记录匹配，但每次运行都会报'Unread result found'错误，不知道原因。附上相关代码，预期匹配成功时输出成功提示，求帮助。

import tkinter as tk
import mysql.connector

class LoginPage(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("Login Page")

        # Username Label and Entry
        username_label = tk.Label(self, text="Username:")
        username_label.pack()
        self.username_entry = tk.Entry(self)
        self.username_entry.pack()

        # Password Label and Entry
        password_label = tk.Label(self, text="Password:")
        password_label.pack()
        self.password_entry = tk.Entry(self, show="*")
        self.password_entry.pack()

        # Login Button
        login_button = tk.Button(self, text="Login", command=self.login_submit())
        login_button.pack()

    def login_submit(self):
        # Database connection configuration
        config = {
            "user": "username",
            "host": "hostname",
            "password": "password",
            "database": "database_name",
            "raise_on_warnings": True
        }

        try:
            db = mysql.connector.connect(**config)
            print("Connection successful")
        except mysql.connector.Error as err:
            print("Something is wrong with your connection")
            print(err)
            return

        # Collecting data from entries
        username = self.username_entry.get()
        password = self.password_entry.get()

        # Creating a cursor
        cursor = db.cursor()

        # Query to select matching username and password from the main_db table
        sql = f"SELECT * FROM main_db WHERE username = '{username}' AND password = '{password}'"

        try:
            # Execute the SQL query
            cursor.execute(sql)

            # Fetch a single row
            result = cursor.fetchone()

            if result:
                print("Successful")
            else:
                print("Nope")

        except mysql.connector.Error as err:
            print("Error occurred during query execution")
            print(err)

        # Close the database connection
        db.close()

if __name__ == "__main__":
    login_page = LoginPage()
    login_page.mainloop()

问题原因及解决方法 #

1. 按钮绑定错误 #

你在绑定登录按钮的command参数时，直接调用了self.login_submit()，这会导致程序初始化时就执行这个方法，而非点击按钮时触发。正确写法是传入方法名（不带括号）：

login_button = tk.Button(self, text="Login", command=self.login_submit)

2. SQL注入风险与查询写法问题 #

用字符串格式化拼接SQL语句不仅存在严重的SQL注入漏洞，还可能引发'Unread result found'错误。必须改用参数化查询：

sql = "SELECT * FROM main_db WHERE username = %s AND password = %s"
cursor.execute(sql, (username, password))

3. 未读取的结果集 #

当游标存在未读取的结果时，会触发该错误。可以在创建游标时指定buffered=True，确保结果被正确读取：

cursor = db.cursor(buffered=True)

4. 资源管理不规范 #

建议用with语句管理数据库连接和游标，确保资源自动释放，避免因连接未正确关闭引发的问题。

修正后的完整代码 #

import tkinter as tk
import mysql.connector

class LoginPage(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("登录页")

        # 用户名标签与输入框
        username_label = tk.Label(self, text="用户名:")
        username_label.pack()
        self.username_entry = tk.Entry(self)
        self.username_entry.pack()

        # 密码标签与输入框
        password_label = tk.Label(self, text="密码:")
        password_label.pack()
        self.password_entry = tk.Entry(self, show="*")
        self.password_entry.pack()

        # 登录按钮（修复command绑定）
        login_button = tk.Button(self, text="登录", command=self.login_submit)
        login_button.pack()

    def login_submit(self):
        # 数据库连接配置
        config = {
            "user": "username",
            "host": "hostname",
            "password": "password",
            "database": "database_name",
            "raise_on_warnings": True
        }

        # 获取输入内容
        username = self.username_entry.get()
        password = self.password_entry.get()

        try:
            # 使用with管理连接和游标，自动释放资源
            with mysql.connector.connect(**config) as db:
                with db.cursor(buffered=True) as cursor:
                    # 参数化查询
                    sql = "SELECT * FROM main_db WHERE username = %s AND password = %s"
                    cursor.execute(sql, (username, password))
                    result = cursor.fetchone()

                    if result:
                        print("登录成功")
                    else:
                        print("用户名或密码错误")

        except mysql.connector.Error as err:
            print("数据库操作出错")
            print(err)

if __name__ == "__main__":
    login_page = LoginPage()
    login_page.mainloop()

内容的提问来源于stack exchange，提问作者Zakii