尝试发送包含 MySQL 变量的 MySQL 查询时 Python 返回错误

Question

我正在尝试通过使用 Python 发送 MySQL 查询来从 MySQL 数据库中检索数据。

当我在 MySQL 工作台中发送 MySQL 查询时，它运行得非常好。

当我使用 Python（在 Jupyter Notebook 中）尝试相同的操作时，它会返回错误。

Python 代码：

import pymysql
import pandas as pd

def run_mysql(SQLQ):
    conn = pymysql.connect(host='IP address', user='username', passwd='password', db='database name')
    df = pd.read_sql(SQLQ, conn)
    conn.close()
    return df

mysql_query = '''set @Yesterday = curdate() -1 ;
                SELECT * FROM mt4_daily
                where date(time) = date(@Yesterday)
                '''
df = run_mysql(mysql_query)
display(df)

错误：

DatabaseError: Execution failed on sql 'set @Yesterday = curdate() -1 ;
                SELECT * FROM mt4_daily
                where date(time) = date(@Yesterday)
                ': (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT * FROM mt4_daily\n                where date(time) = date(@Yesterday)' at line 2")

如果我删除 MySQL Query 中的变量，它运行良好：

import pymysql
import pandas as pd

def run_mysql(SQLQ):
    conn = pymysql.connect(host='IP address', user='username', passwd='password', db='database name')
    df = pd.read_sql(SQLQ, conn)
    conn.close()
    return df

mysqlquery = '''SELECT * FROM mt4_daily
                where date(time) = date(curdate() -1)
                '''
df = run_mysql(mysqlquery)
display(df)

我做错了什么？

---

最终解决方案：

感谢Prashant Sharma 的解决方案。

我对其进行了一些调整，使其返回一个 pandas 数据帧，并允许在 Select 查询之前传递一个变量列表。

代码如下：

import pymysql
import pandas as pd

def run_mysql(SQLQ,MySQL_Variable_List=''):
    try:
        conn = pymysql.connect(host='Server IP', user='UserName', passwd='Password', db='Database name')
        cursor = conn.cursor()
        for i in MySQL_Variable_List:
            cursor.execute(i)
        df = pd.read_sql(SQLQ, conn)
    except Exception as e:
        print(str(e))
    finally:
        cursor.close()
        conn.close()
        return df

MySQL_Variable_List = ["set @Yesterday = curdate() -1 ;"]
SQLQ = "SELECT * FROM mt4_daily where date(time) = date(@Yesterday) limit 10"
df1 = run_mysql(MySQL_Variable_List,SQLQ)

display(df1)

Answer 1

下面的代码完成了这项工作，已经测试过了。如果出现问题，您可能需要纠正一些缩进问题。

import pymysql
def run_mysql(query1, query2):
    try:
      conn = pymysql.connect(host='localhost', user='root', passwd='', db='data_new_es')
      cursor = conn.cursor()
      cursor.execute(query1)
      cursor.execute(query2)
      row = cursor.fetchone()
      print(row)
 except Exception as e:
     print(str(e))
 finally:
     cursor.close()
     conn.close()

mysqlquery1 = "set @Yesterday = curdate() -1 ;"
mysqlquery2 = "select * from abcde where date(accrual_date) = 
date(@Yesterday)"
df1 = run_mysql(mysqlquery1,mysqlquery2)

Answer 2

尝试将它们作为两个单独的查询运行。

mysql_query = '''set @Yesterday = curdate() -1 ;'''
df = run_mysql(mysql_query)
mysql_query = '''SELECT * FROM mt4_daily
                where date(time) = date(@Yesterday)
                '''
df = run_mysql(mysql_query)

Answer 3

我想是因为有两个语句，而这个函数只允许同时读取和执行一个。根据pandas read_sql documentetation 可以使用read_sql "params" 关键字参数来解决这个问题，并将@Yesterday 的值计算移到python 端：

import pymysql
import pandas as pd

from datetime import datetime, timedelta

def run_mysql(SQLQ, params):
    conn = pymysql.connect(host='IP address', user='username', passwd='password', db='database name')
    df = pd.read_sql(SQLQ, conn, params=params)
    conn.close()
    return df

mysqlquery = '''SELECT * FROM mt4_daily
                where date(time) = date(%(yesterday)s)
             '''
yesterday = datetime.date(datetime.now())- timedelta(days=1)
params = {'yesterday': yesterday}
df = run_mysql(mysqlquery, params)
display(df)

我无法执行代码，但想法是这样的。