Python MySQL Connector在游标循环中执行第二个sql语句？

Question

以下逻辑适用于mysqldb模块(请参阅python mysqldb一个连接的多个游标),但我在cursor2.execute(sql)上使用mysql.connector收到以下错误

"发现未读结果."

我意识到我可以使用连接来组合这两个简单的sql语句,并避免需要第二个游标,但我的真实世界的例子更复杂,需要第二个sql语句.

假设我需要执行2个单独的sql语句(1个用于循环,1个用于循环),如何使用mysql.connector模块完成？

import datetime
import mysql.connector

db = mysql.connector.connect(user='alan', password='please', host='machine1', database='mydb')

cursor1 = db.cursor()
cursor2 = db.cursor()

sql = """
SELECT userid, 
       username,
       date
  FROM user
 WHERE date BETWEEN %s AND %s
"""

start_date = datetime.date(1999, 1, 1)
end_date   = datetime.date(2014, 12, 31)

cursor1.execute(sql, (start_date, end_date))

for (userid, username, date) in cursor1:

    sql = """
        select count(*)
        from request
        where assigned = '%s'
    """ % (userid)

    cursor2.execute(sql)
    requestcount = cursor2.fetchone()[0]

    print userid, requestcount

cursor2.close()
cursor1.close()
db.close()

这个mysqldb版本工作得很好:

import datetime
import MySQLdb 

db = MySQLdb.connect(user='alan', passwd='please', host='machine1', db='mydb')

cursor1 = db.cursor()
cursor2 = db.cursor()

sql = """
SELECT userid, 
       username,
       date
  FROM user
 WHERE date BETWEEN %s AND %s
"""

start_date = datetime.date(1999, 1, 1)
end_date   = datetime.date(2014, 12, 31)

cursor1.execute(sql, (start_date, end_date))

for (userid, username, date) in cursor1:

    sql = """
        select count(*)
        from request
        where assigned = '%s'
    """ % (userid)

    cursor2.execute(sql)
    requestcount = cursor2.fetchone()[0]

    print userid, requestcount

cursor2.close()
cursor1.close()
db.close()

Answer 1

默认情况下,MySQL Connector/Python是非缓冲的.这意味着不会自动获取数据,您需要"消耗" 所有行.(它适用于MySQLdb,因为默认情况下该驱动程序是缓冲的.)

使用Connector/Python,您必须将buffered-argument设置为True,以用作迭代器.在OP的问题中,这将是cursor1:

cursor1 = db.cursor(buffered=True)
cursor2 = db.cursor()

您还可以使用buffered=Trueas connection参数来通过此连接缓冲实例化所有游标缓冲.