Creating a dynamic SQL Query from Python

Question

I am using the below set of parameters to create a dynamic sql query and running it from python.

target_column = 'connect_status'
table_name = 'public.main_table'

query_params = {'month_date' : '201801',
                'churn_date' : ['201802','201803','201804'],
                'disco_target' : '1-3 Month Disco'
                }


for churn in query_params['churn_date']:
    sql_data_sample = str("""select * from {1}
                                where dt = %(month_date)s 
                                and churn_date = %(churn)s
                                and {0} IN (%(disco_target)s,'No Disco') order by random() limit 5000
                                ;""").format(target_column,table_name)
    print (sql_data_sample)


    df_data_sample = pd.read_sql(sql_data_sample,con = cnxn,params = query_params)

However this gives an DatabaseError:

Execution failed on sql 'select * from public.main_table
                                where dt = %(month_date)s 
                                and churn_date = %(churn)s
                                and connect_status IN (%(disco_target)s,'No Disco') order by random() limit 5000
                                ;': 'churn'

Can someone please help me to correct this?

Anoop Kumar · Accepted Answer · 2018-11-12 07:02:25Z

The problem is because churn is not available in query_params. Modify your code to

for churn in query_params['churn_date']:
    try:
       sql_data_sample = str("""select * from {1}
                            where dt = %(month_date)s 
                            and churn_date = %(churn)s
                            and {0} IN (%(disco_target)s,'No Disco') order by random() limit 5000
                            ;""").format(target_column,table_name)
        print (sql_data_sample)

        query_params['churn'] = churn
        df_data_sample = pd.read_sql(sql_data_sample,con = cnxn,params = query_params)
    except (Exception, psycopg2.DatabaseError) as error:
        print(error)

Patrik Iselind · Accepted Answer · 2018-11-12 06:25:26Z

1

Your string format expression references data in your query_params but query_params isn't referenced in the format function's parameters. Have a look at your month_date and disco_target usage.

answered Nov 12, 2018 at 6:25

Patrik Iselind

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Jeremy Caney · Accepted Answer · 2022-09-01 06:30:48Z

#Use this python to write the dynamic update query for postgreSql

def updateQuery(self,tableName,setFields,setValues,whereFields,whereValues):

    querySetfields = None
    queryWhereFields = None

    # Loop for set fields
    for i in range(len(setFields)):
        if querySetfields is None:
            querySetfields=setFields[i]+"='"+setValues[i]+"'"
        else:
            querySetfields=querySetfields+","+setFields[i]+"='"+setValues[i]+"'"
    
    # Loop for whereFields
    for i in range(len(whereFields)):
        if queryWhereFields is None:
            queryWhereFields=whereFields[i]+"='"+whereValues[i]+"'"
        else:
            queryWhereFields=queryWhereFields+","+whereFields[i]+"='"+whereValues[i]+"'"
    
    #Form the complete update query
    query="UPDATE "+tableName+" SET "+querySetfields+" WHERE "+queryWhereFields
    
    return query

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