Question

当我在MySQL Workbench中运行查询时，我收到11个结果（如预期的那样），但是当我使用python-mysql.connector运行完全相同的查询时，我得到0结果。知道怎么可能吗？

我已启用query_time = 0的慢速日志来记录每个查询的详细信息。

使用MySQL Workbench进行查询：

# Time: 2016-07-24T16:09:29.154764Z
# User@Host: root[root] @ localhost [127.0.0.1]  Id:     4
# Query_time: 0.007341  Lock_time: 0.000326 Rows_sent: 11  Rows_examined: 536
SET timestamp=1469376569;
SELECT rank, IF(rank>10,NULL,ccy) AS ccy, SUM(req_count)
    FROM (
      SELECT @rank := (@rank := @rank+1) AS rank, ccy, req_count
      FROM (
        SELECT want_currency AS ccy, COUNT(*) AS req_count
        FROM stage.data_tracking
        WHERE user_location LIKE '%Singapore%' AND
          search_country = 'SG' AND
          have_currency = 'SGD' AND
          want_currency != 'SGD' AND
          amount_usd != 1000
        GROUP BY want_currency
        ORDER BY req_count DESC
      ) AS d1
    ) AS d2
    CROSS JOIN (SELECT @rank := 0) AS param
      WHERE rank IS NOT NULL
    GROUP BY LEAST(rank, 11);

的Python：

# Time: 2016-07-24T16:01:12.230648Z
# User@Host: root[root] @ localhost [127.0.0.1]  Id:    11
# Query_time: 0.003171  Lock_time: 0.000188 Rows_sent: 0 Rows_examined: 514
SET timestamp=1469376072;
SELECT rank, IF(rank>10,NULL,ccy) AS ccy, SUM(req_count)
    FROM (
      SELECT @rank := (@rank := @rank+1) AS rank, ccy, req_count
      FROM (
        SELECT want_currency AS ccy, COUNT(*) AS req_count
        FROM stage.data_tracking
        WHERE user_location LIKE '%Singapore%' AND
          search_country = 'SG' AND
          have_currency = 'SGD' AND
          want_currency != 'SGD' AND
          amount_usd != 1000
        GROUP BY want_currency
        ORDER BY req_count DESC
      ) AS d1
    ) AS d2
    CROSS JOIN (SELECT @rank := 0) AS param
      WHERE rank IS NOT NULL
    GROUP BY LEAST(rank, 11);

据我所知，这些查询是相同的，但发送的行数和检查的行数仍然不同。

我的Python代码很简单：

config = {
  'user': os.environ.get("DB_USERNAME"),
  'password': os.environ.get("DB_PASSWORD"),
  'host': os.environ.get("DB_HOST"),
  'database': os.environ.get("DB_DATABASE"),
  'raise_on_warnings': True,
  'buffered': True,
}

try:
  conn = mysql.connector.connect(**config)
except mysql.connector.Error as err:
  if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
    raise
  elif err.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
    raise
  else:
    print(err)
    raise

query = """
  SELECT rank, IF(rank>10,NULL,ccy) AS ccy, SUM(req_count)
  FROM (
    SELECT @rank := (@rank := @rank+1) AS rank, ccy, req_count
    FROM (
      SELECT want_currency AS ccy, COUNT(*) AS req_count
      FROM stage.data_tracking
      WHERE user_location LIKE %s AND
        search_country = %s AND
        have_currency = %s AND
        want_currency != %s AND
        amount_usd != 1000
      GROUP BY want_currency
      ORDER BY req_count DESC
    ) AS d1
  ) AS d2
  CROSS JOIN (SELECT @rank := 0) AS param
    WHERE rank IS NOT NULL
  GROUP BY LEAST(rank, 11)
"""

params = ("%Singapore%", "SG", "SGD", "SGD")

cursor = conn.cursor()
cursor.execute(query, params)
row = cursor.fetchone()
print(row)
while row is not None:
  print(row)
  row = cursor.fetchone()

我尝试添加/删除连接参数（如缓冲），fetchall而不是fetchone，不同的mysql用户。

我正在跑步：

python 3.5.2
python-mysql.connector 2.0.4
mysql 5.7.13

更新

找到了解决方法！如果我将代码更改为：

cursor = conn.cursor()
cursor.execute(query, params)
cursor.close()
cursor = conn.cursor()
cursor.execute(query, params)
row = cursor.fetchone()
print(row)
while row is not None:
  print(row)
  row = cursor.fetchone()

然后会显示正确的结果！什么会导致这种行为？这会是python.mysql-connector中的错误吗？

Python MySQL.connector与MySQL Workbench的结果不同

0 个答案: