根据python中的多个条件以及日期字段从访问表中删除行

Question

我正在尝试从 access 数据库表中删除行，基于两列，一列是 release_by 和 release_date。

Sudo code

WHERE released_by  = '27' and released_date would change based on the day of the month. 

Released_Date 如果 day ==1 然后删除上个月的数据，否则删除当前月份的数据。

import pandas as pd
import numpy as np
import datetime
from datetime import date
from datetime import datetime, timedelta
from dateutil.relativedelta import relativedelta
import pyodbc
import calendar
import xlrd
import defusedxml
from defusedxml.common import EntitiesForbidden
from xlrd import open_workbook
defusedxml.defuse_stdlib()

# connecting to access database
conn = pyodbc.connect(r'Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=C:\Users\Desktop\Insights.accdb;')
insights_dbcurs = conn.cursor()

select_auto_releases = "SELECT * FROM RELEASES WHERE RELEASED_BY = '27'"
autoreleases = insights_dbcurs.execute(select_auto_releases).fetchall()
#display(autoreleases)

for row in autoreleases:
    previousmonth = datetime.now() - relativedelta(months=1)
    previousmonth = previousmonth.strftime("%m - %Y")
    currentmonth = datetime.now()
    currentmonth = currentmonth.strftime("%m - %Y")
    if ((row.autoreleases['RELEASED_DATE']).strftime) ==1:
        try:
            delete = 'DELETE * FROM RELEASES WHERE RELEASED_DATE = ? and RELEASED_BY = ?'
            insights_dbcurs.execute(delete,{'RELEASED_DATE':currentmonth},{'RELEASED_BY':'27'})
        except:
            delete = 'DELETE * FROM RELEASES WHERE RELEASED_DATE = ? and RELEASED_BY = ?'
            insights_dbcurs.execute(delete,{'RELEASED_DATE':previousmonth},{'RELEASED_BY':'27'})

insights_dbcurs.close()
conn.commit()
conn.close()

它不起作用。我明白了：

AttributeError: 'pyodbc.Row' 对象没有属性 'autoreleases'

如果我删除Row.autorelease，我会得到

sql有0个属性，2个被传递。

我该如何避免这种情况。任何建议都会很有帮助。

Answer 1

考虑针对几个问题重构您的代码：

1. try/except 通常用于处理运行时异常和错误，而不是应用程序逻辑。在这些情况下使用if/else。

2. 删除不需要的 for 循环，因为您不会逐行删除，因为没有唯一标识符被传递到 DELETE 语句中。实际上，如果逻辑将未过滤的当前行传递给该行，则您正在跨整个表运行删除过程。

3. 将纯 SQL 与一个 DELETE 语句一起使用，避免 Python 处理时间元素，如您所见，这会维护数据库的转换问题。 MS Access SQL 确实具有日期函数，例如 Date()（当前日期）和 DatePart() 用于月/日提取。此外，MS Access 可以在DELETE 中运行复杂的子查询逻辑。

SQL

对两个日期条件都使用IN 子查询。注意：ID 应替换为表的唯一标识符。在DELETE 版本之前检查SELECT 查询版本。

DELETE FROM RELEASES r
WHERE r.ID IN
  (SELECT sub.ID  
   FROM RELEASES sub
   WHERE sub.RELEASED_BY = ? 
     AND (
           (
            DatePart('m', sub.RELEASED_DATE) = DatePart('m', Date()) - 1
            AND DatePart('yyyy', sub.RELEASED_DATE) = DatePart('yyyy', Date())
            AND DatePart('d', sub.RELEASED_DATE) = 1
           )
          OR 
           (
            DatePart('m', sub.RELEASED_DATE) = DatePart('m', Date())
            AND DatePart('yyyy', sub.RELEASED_DATE) = DatePart('yyyy', Date())
            AND DatePart('d', sub.RELEASED_DATE) > 1
           )
        )
  )

Python

使用 Access 引擎中处理的日期传递参数。

conn = pyodbc.connect(r'...')
insights_dbcurs = conn.cursor()

sql = """DELETE FROM RELEASES r
         WHERE r.ID IN
           (SELECT sub.ID 
            FROM RELEASES sub
            WHERE sub.RELEASED_BY = ? 
              AND (
                    (
                     DatePart('m', sub.RELEASED_DATE) = DatePart('m', Date()) - 1
                     AND DatePart('yyyy', sub.RELEASED_DATE) = DatePart('yyyy', Date())
                     AND DatePart('d', sub.RELEASED_DATE) = 1
                    )
                   OR 
                    (
                     DatePart('m', sub.RELEASED_DATE) = DatePart('m', Date())
                     AND DatePart('yyyy', sub.RELEASED_DATE) = DatePart('yyyy', Date())
                     AND DatePart('d', sub.RELEASED_DATE) > 1
                    )
                  )
           )"""

insights_dbcurs.execute(sql, ('27',))
conn.commit()
conn.close()