pandas read_sql中的“ TypeError：'NoneType'对象不可迭代”

Question

我正在尝试在python中使用pyodbc运行SQL命令。其中SQL命令包含多个SELECT命令和IF语句。

但我收到如下错误

columns = [col_desc[0] for col_desc in cursor.description]
TypeError: 'NoneType' object is not iterable

import pyodbc
import pandas as pd
conn = pyodbc.connect("DRIVER={SQL Server};"
                "SERVER=server_name;"
                "DATABASE=master;"
                "Trusted_Connection=yes;")
cursor = conn.cursor()
script="""

If object_id ('tempdb..#Temp1')is not null
drop table #Temp1
Select distinct  a1.some_ID into #Temp1
from DOC.dbo.Document_tbl (NOLOCK)a1
from #Temp1 a1
If object_id ('tempdb..#Temp2')is not null
Drop table #Temp2
select distinct v2.some_data
into #Temp2 from tbl_name (nolock) v2

If object_id ('tempdb..#Results')is not null
drop table #Results
select distinct a1.*,b1.####
into #Results
from #Temp1 a1
left join #Temp2 b1 on a1.## = b1.##
Select * from #Results
"""

df = pd.read_sql(script, cnxn)
writer = pd.ExcelWriter('result.xlsx')
df.to_excel(writer, sheet_name ='bar')
writer.save()

Answer 1

包含多个SQL语句的SQL命令文本称为 匿名代码块 。匿名代码块可以返回多个结果，每个结果可以是

• 行数
• 包含零个或多个数据行的结果集，或
• 一个错误。

以下示例失败…

sql = """\
SELECT 1 AS foo INTO #tmp;
SELECT * FROM #tmp;
"""
df = pd.read_sql_query(sql, cnxn)
# TypeError: 'NoneType' object is not iterable

…，因为第一个SELECT ... INTO返回行计数，第二个SELECT返回其结果集。

解决方法是启动匿名代码块，SET NOCOUNT ON;该代码块将抑制行数并仅返回结果集：

sql = """\
SET NOCOUNT ON;
SELECT 1 AS foo INTO #tmp;
SELECT * FROM #tmp;
"""
df = pd.read_sql_query(sql, cnxn)
# no error