Python 进阶（四）：数据库操作之 MySQL
1. 简介
MySQL 是目前使用最广泛的数据库之一，它有着良好的性能，能够跨平台，支持分布式，能够承受高并发。如果还没有安装 MySQL，下载地址：https://dev.mysql.com/downloads/mysql/5.7.html，安装参考：https://jingyan.baidu.com/article/fc07f989b298ca12ffe519b6.html。
Python 大致有如下 5 种方式操作 MySQL。
-
MySQL-python
MySQL-python 也称 MySQLdb，基于 C 库开发，曾经是一个十分流行的 MySQL 驱动，具有出色的性能，但其早已停更，仅支持 Python2，不支持 Python3，现在基本不推荐使用了，取而代之的是它的衍生版。
-
mysqlclient
MySQLdb 的 Fork 版本，完全兼容 MySQLdb，支持 Python3，它是 Django ORM 的依赖工具，如果你喜欢用原生 SQL 操作数据库，那么推荐使用它。
-
PyMySQL
PyMySQL 采用纯 Python 开发，兼容 MySQLdb，性能不如 MySQLdb，安装方便，支持 Python3。
-
peewee
peewee 是一个流行的 ORM 框架，实现了对象与数据库表的映射，兼容多种数据库，我们无需知道原生 SQL，只要了解面向对象的思想就可以简单、快速的操作相应数据库，支持 Python3。
-
SQLAlchemy
SQLAlchemy 是一个 ORM 框架，同时也支持原生 SQL，支持 Python3，它类似于 Java 的 Hibernate 框架。
2. 实际操作
因为 MySQLdb 不支持 Python3，这里我们只介绍其中后 4 中方式的使用，先使用如下建表语句创建一张简单的数据库表。
CREATE TABLE student (
id int(10) AUTO_INCREMENT PRIMARY KEY,
name varchar(255) NOT NULL,
age int(10) NOT NULL
);2.1 mysqlclient
执行 pip install mysqlclient 进行安装，看一下具体操作。
新增
import MySQLdb
connect = MySQLdb.connect(
# 主机
host='localhost',
# 端口号
port=3306,
# 用户名
user='root',
# 密码
passwd='root',
# 数据库名称
db='test',
# 指定字符的编、解码格式
use_unicode=True,
charset='utf8')
# 先获取游标，再进行相应 SQL 操作
cursor = connect .cursor()
# 执行新增 SQL
sql = 'insert into student (name, age) values(%s,%s);'
data = [
('只因', '22'),
('你太美', '23')
]
cursor.executemany(sql, data)
# 提交
connect.commit()
# 关闭
cursor.close()
connect.close()查询
import MySQLdb
connect = MySQLdb.connect(
host='localhost',
port=3306,
user='root',
passwd='root',
db='test',
use_unicode=True,
charset='utf8')
cursor = connect.cursor()
cursor.execute('SELECT * FROM student')
print(cursor.fetchall())
cursor.close()
connect.close()cursor 查看方法
-
fetchone() 获取结果集的下一行
-
fetchmany(size) 获取结果集的下几行务
-
fetchall() 获取结果集中剩下的所有行
修改
import MySQLdb
connect = MySQLdb.connect(
host='localhost',
port=3306,
user='root',
passwd='root',
db='test',
use_unicode=True,
charset='utf8')
cursor = connect.cursor()
cursor.execute("UPDATE student SET name='张四' WHERE id = 1")
connect.commit()
cursor.close()
connect.close()删除
import MySQLdb
connect = MySQLdb.connect(
host='localhost',
port=3306,
user='root',
passwd='root',
db='test',
use_unicode=True,
charset='utf8')
cursor = connect.cursor()
cursor.execute("DELETE FROM student WHERE id = 1")
connect.commit()
cursor.close()
connect.close()2.2 PyMySQL
执行 pip install pymysql 进行安装，使用方式与 mysqlclient 基本类似。
import pymysql
connect = pymysql.connect(
host='localhost',
port=3306,
user='root',
password='root',
database='test',
charset='utf8'
)
cursor = connect.cursor()
sql = 'insert into student (name, age) values(%s,%s);'
data = [
('张三', '22'),
('李四', '23')
]
cursor.executemany(sql, data)
connect.commit()
cursor.execute('SELECT * FROM student')
print(cursor.fetchall())
cursor.close()
connect.close()2.3 peewee
执行 pip install peewee 进行安装，看一下具体操作。
定义映射类
from peewee import *
# 连接数据库
db = MySQLDatabase('test',
host='localhost',
port=3306,
user='root',
passwd='root',
charset='utf8')
# 映射类
class Teacher(Model):
id = AutoField(primary_key=True)
name = CharField()
age = IntegerField()
class Meta:
database = db
# 创建表
db.create_tables([Teacher])新增
from peewee import *
db = MySQLDatabase('test',
host='localhost',
port=3306,
user='root',
passwd='root',
charset='utf8')
class Teacher(Model):
id = AutoField(primary_key=True)
name = CharField()
age = IntegerField()
class Meta:
database = db
t1 = Teacher(name='张三', age=22)
t2 = Teacher(name='李四', age=33)
t3 = Teacher(name='王五', age=33)
t1.save()
t2.save()
t3.save()查询
from peewee import *
db = MySQLDatabase('test',
host='localhost',
port=3306,
user='root',
passwd='root',
charset='utf8')
class Teacher(Model):
id = AutoField(primary_key=True)
name = CharField()
age = IntegerField()
class Meta:
database = db
# 查询单条数据
t = Teacher.get(Teacher.id == 1)
print('name：', t.name)
# 查询多条
ts = Teacher.select().where(Teacher.age == 33)
for t in ts:
print('name：', t.name)修改
from peewee import *
db = MySQLDatabase('test',
host='localhost',
port=3306,
user='root',
passwd='root',
charset='utf8')
class Teacher(Model):
id = AutoField(primary_key=True)
name = CharField()
age = IntegerField()
class Meta:
database = db
t = Teacher.update({Teacher.name: '张四'}).where(Teacher.id == 1)
t.execute()删除
from peewee import *
db = MySQLDatabase('test',
host='localhost',
port=3306,
user='root',
passwd='root',
charset='utf8')
class Teacher(Model):
id = AutoField(primary_key=True)
name = CharField()
age = IntegerField()
class Meta:
database = db
Teacher.delete().where(Teacher.id == 2).execute()2.4 SQLAlchemy
执行 pip install sqlalchemy 进行安装，看一下具体操作。
定义映射类
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
engine = create_engine('mysql+mysqldb://root:root@localhost:3306/test?charset=utf8',
# 打印执行语句
echo=True,
# 连接池大小
pool_size=10,
# 指定时间内回收连接
pool_recycle=3600)
# 映射基类
Base = declarative_base()
# 具体映射类
class Teacher(Base):
# 指定映射表名
__tablename__ = 'teacher'
# 映射字段
id = Column(Integer, primary_key=True)
name = Column(String(30))
age = Column(Integer)
# 创建表
Base.metadata.create_all(engine)新增
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
engine = create_engine('mysql+mysqldb://root:root@localhost:3306/test?charset=utf8',
# 打印执行语句
echo=True,
# 连接池大小
pool_size=10,
# 指定时间内回收连接
pool_recycle=3600)
# 映射基类
Base = declarative_base()
# 具体映射类
class Teacher(Base):
# 指定映射表名
__tablename__ = 'teacher'
# 映射字段
id = Column(Integer, primary_key=True)
name = Column(String(30))
age = Column(Integer)
Session = sessionmaker(bind=engine)
# 创建 Session 类实例
session = Session()
ls = []
t1 = Teacher(name='张三', age=22)
t2 = Teacher(name='李四', age=33)
t3 = Teacher(name='王五', age=33)
ls.append(t1)
ls.append(t2)
ls.append(t3)
session.add_all(ls)
session.commit()
session.close()查询
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
engine = create_engine('mysql+mysqldb://root:root@localhost:3306/test?charset=utf8',
# 打印执行语句
echo=True,
# 连接池大小
pool_size=10,
# 指定时间内回收连接
pool_recycle=3600)
# 映射基类
Base = declarative_base()
# 具体映射类
class Teacher(Base):
# 指定映射表名
__tablename__ = 'teacher'
# 映射字段
id = Column(Integer, primary_key=True)
name = Column(String(30))
age = Column(Integer)
Session = sessionmaker(bind=engine)
# 创建 Session 类实例
session = Session()
# 查询一条数据，filter 相当于 where 条件
t = session.query(Teacher).filter(Teacher.id==1).one()
print('---', t.name)
# 查询所有数据
ts = session.query(Teacher).filter(Teacher.age==33).all()
for t in ts:
print('===', t.name)修改
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
engine = create_engine('mysql+mysqldb://root:root@localhost:3306/test?charset=utf8',
# 打印执行语句
echo=True,
# 连接池大小
pool_size=10,
# 指定时间内回收连接
pool_recycle=3600)
# 映射基类
Base = declarative_base()
# 具体映射类
class Teacher(Base):
# 指定映射表名
__tablename__ = 'teacher'
# 映射字段
id = Column(Integer, primary_key=True)
name = Column(String(30))
age = Column(Integer)
Session = sessionmaker(bind=engine)
# 创建 Session 类实例
session = Session()
t = session.query(Teacher).filter(Teacher.id==1).one()
print('修改前名字-->', t.name)
t.name = '张四'
session.commit()
print('修改后名字-->', t.name)删除
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
engine = create_engine('mysql+mysqldb://root:root@localhost:3306/test?charset=utf8',
# 打印执行语句
echo=True,
# 连接池大小
pool_size=10,
# 指定时间内回收连接
pool_recycle=3600)
# 映射基类
Base = declarative_base()
# 具体映射类
class Teacher(Base):
# 指定映射表名
__tablename__ = 'teacher'
# 映射字段
id = Column(Integer, primary_key=True)
name = Column(String(30))
age = Column(Integer)
Session = sessionmaker(bind=engine)
# 创建 Session 类实例
session = Session()
t = session.query(Teacher).filter(Teacher.id==1).one()
session.delete(t)
session.commit() **最后：下方这份完整的【软件测试】视频学习教程已经整理上传完成，朋友们如果需要可以自行免费领取 【保证100%免费】**
敲字不易，如果此文章对你有帮助的话，点个赞收个藏来个关注，给作者一个鼓励。也方便你下次能够快速查找。
