让Python帮你搞定MySQL数据库

布满荆棘的人生 2022-11-28 13:39 251阅读 0赞

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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。

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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

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好文章，我 在看❤

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