[英]read_sql query returns an empty dataframe after I pass parameters as a dict in python pandas
我正在尝试使用以下字典来参数化SQL查询的某些部分:
query_params = dict(
{'target':'status',
'date_from':'201712',
'date_to':'201805',
'drform_target':'NPA'
})
sql_data_sample = str("""select *
from table_name
where dt = %(date_to)s
and %(target)s in (%(drform_target)s)
----------------------------------------------------
union all
----------------------------------------------------
(select *,
from table_name
where dt = %(date_from)s
and %(target)s in ('ACT')
order by random() limit 50000);""")
df_data_sample = pd.read_sql(sql_data_sample,con = cnxn,params = query_params)
但是,这将返回一个完全没有记录的数据框。 我不确定错误是什么,因为没有错误被抛出。
df_data_sample.shape
Out[7]: (0, 1211)
最终的PostgreSql查询将是:
select *
from table_name
where dt = '201805'
and status in ('NPA')
----------------------------------------------------
union all
----------------------------------------------------
(select *
from table_name
where dt = '201712'
and status in ('ACT')
order by random() limit 50000);-- This part of random() is only for running it on my local and not on server.
以下是用于复制的一小部分数据示例。 原始数据有超过一百万条记录和1211列
service_change_3m service_change_6m dt grp_m2 status
0 -2 201805 $50-$75 NPA
0 0 201805 < $25 NPA
0 -1 201805 $175-$200 ACT
0 0 201712 $150-$175 ACT
0 0 201712 $125-$150 ACT
-1 1 201805 $50-$75 NPA
有人可以帮我吗?
更新:根据@shmee的建议。我最终使用:
target = 'status'
query_params = dict(
{
'date_from':'201712',
'date_to':'201805',
'drform_target':'NPA'
})
sql_data_sample = str("""select *
from table_name
where dt = %(date_to)s
and {0} in (%(drform_target)s)
----------------------------------------------------
union all
----------------------------------------------------
(select *,
from table_name
where dt = %(date_from)s
and {0} in ('ACT')
order by random() limit 50000);""").format(target)
df_data_sample = pd.read_sql(sql_data_sample,con = cnxn,params = query_params)
是的,我非常有信心,您的问题是由于试图通过注释中提到的参数绑定( and %(target)s in ('ACT')
尝试在查询中设置列名而导致的。
这导致查询将结果集限制为记录'status' in ('ACT')
中的'status' in ('ACT')
所在的位置(即字符串'status'是仅包含字符串'ACT'的列表的元素)。 当然,这是错误的,因此不会选择任何记录,并且结果为空。
这应该可以正常工作:
import psycopg2.sql
col_name = 'status'
table_name = 'public.churn_data'
query_params = {'date_from':'201712',
'date_to':'201805',
'drform_target':'NPA'
}
sql_data_sample = """select *
from {0}
where dt = %(date_to)s
and {1} in (%(drform_target)s)
----------------------------------------------------
union all
----------------------------------------------------
(select *
from {0}
where dt = %(date_from)s
and {1} in ('ACT')
order by random() limit 50000);"""
sql_data_sample = sql.SQL(sql_data_sample).format(sql.Identifier(table_name),
sql.Identifier(col_name))
df_data_sample = pd.read_sql(sql_data_sample,con = cnxn,params = query_params)
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