cursor.execute返回1个整数

Question

When running a query to a mysql database using MySqlHook, cursor.execute(query) returns int 1 My code is

import logging
from airflow.hooks.mysql_hook import MySqlHook
query = "SELECT col1, col2 FROM myschema.mytable LIMIT 1"
mysql = MySqlHook(mysql_conn_id=conn_id)
conn = mysql.get_conn()
cursor = conn.cursor()
result_cursor = cursor.execute(query)
logging.info(result_cursor) # this prints out "INFO - 1" in the log
df = pd.DataFrame(result_cursor.fetchall(), columns=result_cursor.keys()) # this triggers error "ERROR - 'int' object has no attribute 'fetchall'"

I would have expected result_cursor to return a "fetchable" result, since the query is working fine.

Answer 1

Cursor.execute() return value is not defined by the db-api spec , but for most implementations it returns the number of rows affected by the query.

To retrieve data, you have to either iterate over the cursor or call .fetchall() .

Answer 2

It seems I cannot save cursor.execute(query) into variable result_cursor. To make the code work, I simply needed to define the data for the data-frame as cursor.fetchall()

cursor.execute(query)
df = pd.DataFrame(list(cursor.fetchall()), column=[col[0] for col in cursor.description])