mysql python上的UPDATE总是返回0作为lastrowid

问题描述

这是我的代码：

def insert_ip_info(instance):
# Cursor to db
cur = db.cursor()

int_ipaddr = ipaddress_string_to_int(instance.ip_address)  # converting the string into unsigned integer

# Check if IP address exits in table (stores results from previous scan)
sql_query = "SELECT * FROM " + ip_info_table_name + " WHERE ip_address = " + str(int_ipaddr)
cur.execute(sql_query)
ip_exists = len(
    cur.fetchall())  # Using the len of the results only, to determine if the IP address exists in the table

if (ip_exists > 0):  # The IP address is already found in the table
    # Update the IP address information in the table
    sql_query = "UPDATE " + ip_info_table_name + \
                " SET hostname = %s , ip_location_id = %s WHERE ip_address = " + str(int_ipaddr)
    sql_data = (instance.hostname, instance.ip_location_id)

else:

    # Write a new line into db
    sql_query = "INSERT INTO " + ip_info_table_name + \
                " (ip_address,hostname,ip_location_id) " + \
                "VALUES(%s,%s,%s);"
    sql_data = (str(int_ipaddr), instance.hostname, instance.ip_location_id)
cur.execute(sql_query, sql_data)
cur.execute('SELECT LAST_INSERT_ID()')
res = cur.fetchone()

cur.execute('SELECT @@identity')
res2 = cur.fetchone()
print cur.lastrowid
print db.insert_id()
print res
print res2
db.commit()

这里是数据库：

Column  Type    Comment
id  int(11) Auto Increment   
ip_address  int(10) unsigned     
hostname    varchar(256) NULL    
ip_location_id  int(11) NULL     
Indexes
PRIMARY id
INDEX   ip_location_id

当我执行INSERT操作时，所有内容都像一个符咒，
，但是当我尝试全部UPDATE操作时4尝试（打印）失败（打印0）。
我不知道我做错了什么。
谢谢

When I make the INSERT operation everything works like a charm,but when I try the UPDATE operation all 4 tries (prints) fail (print 0).I don't have any idea what I made wrong.Thanks

推荐答案

cur.execute('SELECT LAST_INSERT_ID()')

此行说明了一切。无论您是否要求，您正在查看的是最后一个记录 插入 的自动递增的值。当您进行更新时，该索引的自动增量值未更改，因此不会为当前查询生成任何值。

This line says it all. However you request it, what you are looking at is the auto-incremented value of the last record inserted. When you do an update, the auto-increment value for that index has not changed and so there is no value generated for the current query.

仅当您插入新行时有效。如果您想以其他方式获取此值，则可以选择max（id）或查询模式，但这样做实际上没有什么意义。

It's only valid when you have inserted a new row. If you want to obtain this value otherwise then you can either select max(id) or interrogate the schema but there's really very little point in doing so.

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