如何使用存储在变量中的值从 python mysql 数据库中获取特定行？

Posted 2023-03-23

【中文标题】如何使用存储在变量中的值从 python mysql 数据库中获取特定行？

【英文标题】：How can I obtain specific row from python mysql database by using a value stored in a variable?

【发布时间】：2020-12-05 16:34:15

【问题描述】：

我的代码放在这里：

def draw_money():
    dr_list = [acc_num, acc_num_entry, with_btn, with_money,with_money_entry]

    for i in dr_list:
        i.destroy()

    new_acc = acc_num_var.get()
    money_amount = money.get()

    con = pymysql.connect(host="localhost", port=3306, user="root", password="", db="bankac")
    cur = con.cursor()
    query = "SELECT * FROM ac WHERE name = new_acc"
    cur.execute(query)`

但是当我执行这个函数时，我得到了以下错误---

*Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py", line 1705, in __call__    return self.func(*args)
  File "C:\Users\AMISHA SINGH\Documents\app\bank.py", line 33, in draw_money
    cur.execute(query)
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\cursors.py", line 170, in execute
    result = self._query(query)
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\cursors.py", line 328, in _query
    conn.query(q)
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\connections.py", line 517, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\connections.py", line 732, in _read_query_result
    result.read()
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\connections.py", line 1075, in read
    first_packet = self.connection._read_packet()
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\connections.py", line 684, in _read_packet
    packet.check_error()
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\protocol.py", line 220, in check_error
    err.raise_mysql_exception(self._data)
  File "C:\Users\AMISHA SINGH\AppData\Local\Programs\Python\Python37-32\lib\site-packages\pymysql\err.py", line 109, in raise_mysql_exception
    raise errorclass(errno, errval)
pymysql.err.InternalError: (1054, "Unknown column 'new_acc' in 'where clause'")*

请帮助我。我尝试了很多方法，但我无法弄清楚。我正在使用 python 模块 tkinter 和 pymysql 进行银行模拟。我想通过比较存储在 python 变量中的值从数据库中获取特定行。

【参考方案1】：

您需要使用参数替换来传递变量，如下所示：

query = "SELECT * FROM ac WHERE name = %s"
cur.execute(query, (new_acc,))

请注意，传递给执行的值参数必须是元组或列表中的一个，即使只有其中一个。 (new_acc,) 是一个单元素元组。

也可以在字典中传递值，使用稍有不同的替换：

query = "SELECT * FROM ac WHERE name = %(var_name)s"
cur.execute(query, 'var_name': new_acc)

【讨论】：

但是如果有多个项目，那么元组不是必需的吗？

@CoolCloud 不，你仍然需要一个元组/列表：cur.execute(query, (val1, val2))。 cur.execute(query, val1, val2) 产生 TyeError。

不是那样的，比如说values = val1,val2然后cur.execute(query, values))