让Python帮你搞定MySQL数据库

Mysql是常用的数据库之一，也是面试工作必备技能之一。

本文通过一个实战，将Python与Sql语句结合起来使用，搞定MySQL数据库。

// 实战开始 //

我们在github上下载fifa18球员数据，将这些信息存入到mysql。

①数据下载地址：

https://github.com/amanthedorkknight/fifa18-all-player-statistics

②选择：Complete->basicplayerdata.csv

// 将数据从CSV导入到MySQL //

1）创建对应库与表

#创建公司数据库，编码格式utf-8
CREATE DATABASE fifa18_db DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
#选择数据库：
use fifa18_db;
#创建球员表：id,名称，海报地址，俱乐部，年龄，薪资等，与csv文件对应
create table player(id int Primary key auto_increment, 
player_id int, name char(64), age int, poster char(64),


                    flag char(64), overall int, potential int, club char(64) default '', club_Logo char(64), 
                   value char(16), wage char(16), special int) default charset =utf8;

2）CSV读取文件

数据集中某些球员字段为空，插入时候需要补充默认值，使用DictReader读取。

path = '/home/linux/workdir/data/basicplayerdata.csv'
#字段名称
field = ['','ID','Name','Age','Photo','Nationality','Flag','Overall','Potential','Club','Club Logo','Value','Wage','Special']
f = open(path)
fcsv = csv.DictReader(f, fieldnames = field)
#第一行去掉
line = next(fcsv)
#第一行有效数据
line = next(fcsv)
print(line)

结果：

OrderedDict([('', '0'), ('ID', '158023'), ('Name', 'L. Messi'), ('Age', '30'), 
('Photo', 'https://cdn.sofifa.org/players/4/18/158023.png'), ('Nationality', 'Argentina'), 
('Flag', 'https://cdn.sofifa.org/flags/52.png'), 
('Overall', '94'), ('Potential', '94'), ('Club', 'FC Barcelona'), 
('Club Logo', 'https://cdn.sofifa.org/teams/2/18/light/241.png'), 
('Value', '€118.5M'), ('Wage', '€565K'), ('Special', '2161')])

3）读取一行并整理数据格式

CSV读取字段与数据库对应起来，且不要CSV文件种的第一列，整理数据格式为字典，key为数据库列名，value为CSV对应内容，代码实现。

sqlfield = ['player_id','name','age','poster','nationality','flag','overall','potential','club','club_logo','value','wage','special']
csvfield = ['ID','Name','Age','Photo','Nationality','Flag','Overall','Potential','Club','Club Logo','Value','Wage','Special']
#转成字典：
keysinfo = dict(zip(sqlfield, csvfield))
#填充数据：
data = {}
for sfield, cfield in keysinfo.items():
    ele = line.get(cfield, '')
    data.setdefault(sfield, ele)
print(data)

结果：

{'player_id': '158023', 'name': 'L. Messi', 'age': '30', 'poster': 'https://cdn.sofifa.org/players/4/18/158023.png', 
'nationality': 'Argentina', 'flag': 'https://cdn.sofifa.org/flags/52.png', 
'overall': '94', 'potential': '94', 'club': 'FC Barcelona', 
'club_logo': 'https://cdn.sofifa.org/teams/2/18/light/241.png', 
'value': '€118.5M', 'wage': '€565K', 'special': '2161'}

4）拼接sql语句

尝试插入一条数据：获取插入字段与对应数据，拼接成sql语句。

tablename = 'player'
keys = data.keys()
fields = ','.join(keys)
vals = ','.join(["'%s'"% val for val in data.values()])
sql = f"INSERT INTO {tablename}({fields}) VALUES({vals})"
print(sql)

结果：

INSERT INTO player(player_id,name,age,poster,nationality,flag,overall,potential,club,club_logo,value,wage,special) 
VALUES('158023','L. Messi','30','https://cdn.sofifa.org/players/4/18/158023.png','Argentina','https://cdn.sofifa.org/flags/52.png','94','94','FC Barcelona','https://cdn.sofifa.org/teams/2/18/light/241.png','€118.5M','€565K','2161')

5）连接数据库，并插入数据

#编码格式：utf-8
db = pymysql.connect("localhost","root","abc123","fifa18_db", charset='utf8')
#获取游标
cursor = db.cursor()
cursor.execute(sql)
#提交数据
db.commit()
#断开连接
cursor.close()
db.close()

查看player中信息，插入成功。

基本功能都已经实现，对代码进行整理，根据功能定义类及方法。

import csv
import pymysql
class LoadDataFromCsvToMysql:
    def __init__(self, csvpath, csvfield, mysqlfield, table, sqlconfig):
        #初始化参数
        pass
    def connectSql(self):
        #连接数据库，获取游标
        pass
    def disconnectSql(self):
        #断开数据库，获取游标
        pass
    def processSql(self, sql):
        #处理sql语句
        pass
    def loadCsv(self):
        #打开csv文件，返回csv对象
        pass
    def closeCsv(self):
        #关闭csv文件
        pass
    def gensql(self, linedata):
        #生成sql语句
        pass
    def process(self):
        #对外接口，打开文件并写数据库
        pass

类定义完成之后，我们可以将功能明确的方法实现。

import csv
import pymysql
class LoadDataFromCsvToMysql:
    def __init__(self, csvpath, csvfield, mysqlfield, table, sqlconfig):
        #初始化参数
        self.dbconfig = sqlconfig
        self.inpath = csvpath
        self.sqlfield =  mysqlfield
        self.csvfield = csvfield
        self.fieldmap = dict(zip(mysqlfield, csvfield[1:]))
        self.tablename = table
    def connectSql(self):
        self.db = pymysql.connect(**self.dbconfig, charset='utf8')
        self.cursor = self.db.cursor()
    def disconnectSql(self):
        self.cursor.close()
        self.db.close()
    def processSql(self, sql):
        ret = self.cursor.execute(sql)
        self.db.commit()
        return ret
    def loadCsv(self):
        #打开csv文件
        self.f = open(path)
        fcsv = csv.DictReader(self.f, fieldnames = self.csvfield)
        next(fcsv)
        return fcsv
    def closeCsv(self):
        self.f.close()
    def gensql(self, linedata):
        pass
    def process(self):
        #测试数据库与csv文件打开关闭
        self.connectSql()
        print('connect sql...')
        fcsv = self.loadCsv()
        self.disconnectSql()
        self.closeCsv()
        print('disconnect sql')        path = '/home/linux/workdir/data/basicplayerdata.csv'
sqlfield= ['player_id','name','age','poster','nationality','flag','overall','potential','club','club_logo','value','wage','special']
csvfield = ['','ID','Name','Age','Photo','Nationality','Flag','Overall','Potential','Club','Club Logo','Value','Wage','Special']
dbconfig = {'host':'localhost','port':3306,'user':'root','passwd':'abc123','db':'fifa18_db'}
obj = LoadDataFromCsvToMysql(path, csvfield, sqlfield,  'player', dbconfig)
obj.process()

输出：

connect sql...
load csvfile
disconnect sql

6）完善process与gensql

先完善process方法实现：

 def process(self):
        #测试数据库与csv文件打开关闭
        self.connectSql()
        print('connect sql...')
        fcsv = self.loadCsv()
        for line in fcsv:
            sql = self.gensql(line)
            print(sql)
            n = self.processSql(sql)
        self.disconnectSql()
        self.closeCsv()
        print('disconnect sql')

然后完善gensql方法，将前面实现添加到此方法中。

def gensql(self, linedata):
        #产生sql语句
        data = {}
        for sfield, cfield in self.fieldmap.items():
            ele = linedata.get(cfield, '')
            data.setdefault(sfield, ele)
        tablename = self.tablename
        keys = data.keys()
        fields = ','.join(keys)
        vals = ','.join(["'%s'"% val for val in data.values()])
        sql = f"INSERT INTO {tablename}({fields}) VALUES({vals})"
        return sql

测试前将player表中内容删除，然后使用代码先插入一条，并查看结果；如果测试没有问题，可以插入所有数据。实际运行出现问题：sql语句错误 ，字符串拼接错误。

出错sql语句：

"('158023','L. Messi','30','https://cdn.sofifa.org/players/4/18/158023.png',..)"

双引号+单引号，但是文件中，某些字符串带单引号，所以出现字段错误。

修改sql拼接方法：

    def gensql(self, linedata):
        #产生sql语句
        data = {}
        for sfield, cfield in self.fieldmap.items():
            ele = linedata.get(cfield, '')
            data.setdefault(sfield, ele)
        tablename = self.tablename
        keys = data.keys()
        fields = ','.join(keys)
        vals = ','.join(['"%s"'% val for val in data.values()])
        sql = f'INSERT INTO {tablename}({fields}) VALUES({vals})'
        return sql

运行结果：

dstram","18","https://cdn.sofifa.org/players/4/18/238813.png","England","https://cdn.sofifa.org/flags/14.png","47","65","Crewe Alexandra","https://cdn.sofifa.org/teams/2/18/light/121.png","€60K","€1K","1305")
INSERT INTO player(player_id,name,age,poster,nationality,flag,overall,potential,club,club_logo,value,wage,special) 
VALUES("238306","A. Conway","19","https://cdn.sofifa.org/players/4/18/238306.png","Republic of Ireland","https://cdn.sofifa.org/flags/25.png","47","63","Galway United","https://cdn.sofifa.org/teams/2/18/light/1571.png","€60K","€1K","1314")
disconnect sql
1555235373.5942054 1555235392.2122808

插入18000条数据，花费时间大概为20S左右；后续优化：每次插入500条数据，然后在查看花费时间，这个大家可以参考前面案例自己实现。

// 在SQL中查询数据 //

需求：查询player表中阿根廷国家球员姓名，年龄，头像信息。读者朋友可以自己尝试去实现，考虑使用继承。

①sql中查询数据我们步骤：连接数据库，执行sql语句，关闭数据库；

②查询与写入很多方法通用，考虑继承LoadDataFromCsvToMysql类；

③需要重载init，process，processSql方法；

代码实现：

class QueryMysql(LoadDataFromCsvToMysql):
    def __init__(self, sqlconfig):
        #调用父类方法，初始化传一些无效参数
        super(QueryMysql, self).__init__('',[], [], '', dbconfig)
    def genSql(self, table, fields, condition=None):
        #查询语句生成
        fds = ','.join(fields)
        cond = ''
        print(condition)
        if condition:
            cond = f' where {condition}'
        sql = f'select {fds} from {table}{cond}'
        return sql
    def process(self, tablename, fields, condition=None):
        #对外接口
        #调用父类中的连接数据库，关闭数据库方法
        self.connectSql()
        sql = self.genSql(tablename, fields, condition)
        self.processSql(sql)
        items = self.cursor.fetchall()
        for item in items:
            print(item)
        print('all Argentina player:', len(items))
        self.disconnectSql()        dbconfig= {'host':'localhost','port':3306,'user':'root','passwd':'abc123','db':'fifa18_db'}
tablename = 'player'
files = ['name','poster', 'age']
obj = QueryMysql(dbconfig)
cond = 'nationality="Argentina"'
obj.process(tablename, files, cond)

结果：

('L. Messi', 'https://cdn.sofifa.org/players/4/18/158023.png', 30)
('G. Higuaín', 'https://cdn.sofifa.org/players/4/18/167664.png', 29)
('P. Dybala', 'https://cdn.sofifa.org/players/4/18/211110.png', 23)...('A. Miño', 'https://cdn.sofifa.org/players/4/18/243298.png', 23)
('T. Durso', 'https://cdn.sofifa.org/players/4/18/240955.png', 18)
('K. Humeler', 'https://cdn.sofifa.org/players/4/18/240291.png', 20)
('J. Mendive', 'https://cdn.sofifa.org/players/4/18/241584.png', 20)
all Argentina player: 966

结果：

数据集中一共有966名Argentina球员。

转载自:https://blog.csdn.net/LG_227/article/details/105148841

好文章，我 在看❤