如何在 python 中使用单个 MySQL 查询更新多行？

Question

#!/usr/bin/python

# -*- coding: utf-8 -*-
import MySQLdb as mdb

con = mdb.connect('localhost', 'root', 'root', 'kuis')

with con:

    cur = con.cursor()
    cur.execute("UPDATE Writers SET Name = %s WHERE Id = %s ",
        ("new_value" , "3"))
    print "Number of rows updated:",  cur.rowcount

使用上面的代码，数据库中 table Writers 的第三行的值 kuis 被更新为 new_value 并且输出将是 Number od rows更新：1
我应该如何同时更新多行？

Answer 1

可能您正在寻找 cursor.executemany。

cur.executemany("UPDATE Writers SET Name = %s WHERE Id = %s ",
        [("new_value" , "3"),("new_value" , "6")])

Answer 2

我认为 mysqldb 无法同时处理多个 UPDATE 查询。

但是您可以使用最后带有 ON DUPLICATE KEY UPDATE 条件的 INSERT 查询。

为了易用性和可读性，我写了下面的例子。

import MySQLdb

def update_many(data_list=None, mysql_table=None):
    """
    Updates a mysql table with the data provided. If the key is not unique, the
    data will be inserted into the table.

    The dictionaries must have all the same keys due to how the query is built.

    Param:
        data_list (List):
            A list of dictionaries where the keys are the mysql table
            column names, and the values are the update values
        mysql_table (String):
            The mysql table to be updated.
    """

    # Connection and Cursor
    conn = MySQLdb.connect('localhost', 'jeff', 'atwood', 'Whosebug')
    cur = conn.cursor()

    query = ""
    values = []

    for data_dict in data_list:

        if not query:
            columns = ', '.join('`{0}`'.format(k) for k in data_dict)
            duplicates = ', '.join('{0}=VALUES({0})'.format(k) for k in data_dict)
            place_holders = ', '.join('%s'.format(k) for k in data_dict)
            query = "INSERT INTO {0} ({1}) VALUES ({2})".format(mysql_table, columns, place_holders)
            query = "{0} ON DUPLICATE KEY UPDATE {1}".format(query, duplicates)

        v = data_dict.values()
        values.append(v)

    try:
        cur.executemany(query, values)
    except MySQLdb.Error, e:
        try:
            print"MySQL Error [%d]: %s" % (e.args[0], e.args[1])
        except IndexError:
            print "MySQL Error: %s" % str(e)

        conn.rollback()
        return False

    conn.commit()
    cur.close()
    conn.close()

一行解释

columns = ', '.join('`{}`'.format(k) for k in data_dict)

与

相同

column_list = []
for k in data_dict:
    column_list.append(k)
columns = ", ".join(columns)

这是一个用法示例

test_data_list = []
test_data_list.append( {'id' : 1, 'name' : 'Tech', 'articles' : 1 } )
test_data_list.append( {'id' : 2, 'name' : 'Jhola', 'articles' : 8 } )
test_data_list.append( {'id' : 3, 'name' : 'Wes', 'articles' : 0 } )

update_many(data_list=test_data_list, mysql_table='writers')

查询输出

INSERT INTO writers (`articles`, `id`, `name`) VALUES (%s, %s, %s) ON DUPLICATE KEY UPDATE articles=VALUES(articles), id=VALUES(id), name=VALUES(name)

值输出

[[1, 1, 'Tech'], [8, 2, 'Jhola'], [0, 3, 'Wes']]

Answer 3

我必须写一个简单的供我使用的是。

sql='''INSERT INTO <Tabel Name> (column 1, column 2, ... , column N)
 VALUES (%s, %s, ..., %s) 
ON DUPLICATE KEY UPDATE column1=VALUES(column 1), column3=VALUES(column N)'''

mycursor.executemany(sql, data)

数据 = ['value of column 1', 'value of column 2' , ... ,'value of column N']

如何在 python 中使用单个 MySQL 查询更新多行？

How to update multiple rows with single MySQL query in python?

python

mysql

mysql-python