python propresql mysql_Python操作MySQL：pymysql和SQLAlchemy

大家好，我是讯享网，很高兴认识大家。

本篇对于Python操作MySQL主要使用两种方式：

原生模块 pymsql

ORM框架 SQLAchemy

pymsql

pymsql是Python中操作MySQL的模块，其使用方法和MySQLdb几乎相同。

下载安装

pip3 install pymysql

使用操作

1、执行SQL

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

# 创建连接

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

# 创建游标

cursor = conn.cursor()

# 执行SQL，并返回收影响行数

effect_row = cursor.execute("update hosts set host = '1.1.1.2'")

# 执行SQL，并返回受影响行数

#effect_row = cursor.execute("update hosts set host = '1.1.1.2' where nid > %s", (1,))

# 执行SQL，并返回受影响行数

#effect_row = cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)])

# 提交，不然无法保存新建或者修改的数据

conn.commit()

# 关闭游标

cursor.close()

# 关闭连接

conn.close()

示例:

import pymysql

conn = pymysql.connect(host="10.37.129.3",port=3306,user="egon",passwd="",db="homework",charset="utf8")

cursor = conn.cursor()

#方式一:

sql = "select * from course where cid=1"

effect_row = cursor.execute(sql)

# 方式二：

sql = "select * from course where cid='%s'" %(1,)

effect_row = cursor.execute(sql)

# 方式三普通列表

sql = "select * from course where cid='%s'"

effect_row = cursor.execute(sql,1)

effect_row = cursor.execute(sql,[1])

# 方式四字典格式

sql = "select * from course where cid='%(u)s'"

effect_row = cursor.execute(sql,{"u":1})

row_1 = cursor.fetchone()

cursor.close()

conn.close()

print(row_1)

2、获取新创建数据自增ID

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

cursor = conn.cursor()

cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)])

conn.commit()

cursor.close()

conn.close()

# 获取最新自增ID

new_id = cursor.lastrowid

3、获取查询数据

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

cursor = conn.cursor()

cursor.execute("select * from hosts")

# 获取第一行数据

row_1 = cursor.fetchone()

# 获取前n行数据

# row_2 = cursor.fetchmany(3)

# 获取所有数据

# row_3 = cursor.fetchall()

conn.commit()

cursor.close()

conn.close()

注：在fetch数据时按照顺序进行，可以使用cursor.scroll(num,mode)来移动游标位置，如：

cursor.scroll(1,mode='relative') # 相对当前位置移动

cursor.scroll(2,mode='absolute') # 相对绝对位置移动

4、fetch数据类型

关于默认获取的数据是元祖类型，如果想要或者字典类型的数据，即：

#!/usr/bin/env python

# -*- coding:utf-8 -*-

import pymysql

conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')

# 游标设置为字典类型

cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)

r = cursor.execute("call p1()")

result = cursor.fetchone()

conn.commit()

cursor.close()

conn.close()

5、插入演示

import pymysql

conn = pymysql.connect(host="10.37.129.3",port=3306,user="egon",passwd="",db="student_info",charset="utf8")

cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)

#插入一行

# sql = "insert into student_info(sname,gender,class_id) VALUES('alex1','女',2)"

#插入多行

sql = "insert into student_info(sname,gender,class_id) VALUES('alex1','女',2),('alex2','女',2),('alex3','女',2)"

r = cursor.execute(sql)

#或

sql = "insert into userinfo(username,password) values(%s,%s)"

# 受影响的行数

r = cursor.executemany(sql,[('egon','sb'),('laoyao','BS')])

conn.commit()

cursor.close()

conn.close()

print(r)

6、补充

# sql 注入

import pymysql

user = input("username:")

pwd = input("password:")

conn = pymysql.connect(host="localhost",user='root',password='',database="db3") #建立与客户端的链接

cursor = conn.cursor()

sql = "select * from userinfo where username='%s' and pwd='%s'" %(user,pwd,) #不要自己定义放置占位符user和pwd，防数据库被泄露

# select * from userinfo where username='uu' or 1=1 -- ' and password='%s'

#上面部分会理解成，第一部分：select * from userinfo where username='uu'，第二部分：or 1=1，第三部分：-- 注释，

# 第四部分：' and password='%s'，第四部分会当成注释内容。所以执行该程序会显示登录成功。

cursor.execute(sql) #执行sql语句

result = cursor.fetchone() #返回第一行内容

#关闭连接

cursor.close()

conn.close()

if result:

print('登录成功')

else:

print('登录失败')

import pymysql

user = input("username:")

pwd = input("password:")

conn = pymysql.connect(host="localhost",user='root',password='',database="db3")

cursor = conn.cursor()

sql = "select * from userinfo where username=%s and pwd=%s"

# cursor.execute(sql,(user,pwd))

cursor.execute(sql,[user,pwd]) #cursor.execute(sql,user,pwd)也可写成cursor.execute(sql,[user,pwd])，效果一样

# cursor.execute(sql,{'u':user,'p':pwd}) #sql中加入key值，打印结果就会变成字典的格式而不是元组格式

result = cursor.fetchone() #取一行

cursor.close()

conn.close()

if result:

print('登录成功')

else:

print('登录失败')

print(result)

import pymysql

# 增加，删，该

#增

# conn = pymysql.connect(host="localhost",user='root',password='',database="db3")

# cursor = conn.cursor()

# sql = "insert into userinfo(username,pwd) values('root','')"

# 受影响的行数

# r = cursor.execute(sql)

# #

# conn.commit() #对数据库有改变均要执行conn.commit()命令，提交给数据库。所以增删改均需有这条命令，查不需要。

# cursor.close()

# conn.close()

# conn = pymysql.connect(host="localhost",user='root',password='',database="db3")

# cursor = conn.cursor()

# # sql = "insert into userinfo(username,pwd) values(%s,%s)"

# # cursor.execute(sql,(user,pwd,))

# sql = "insert into userinfo(username,password) values(%s,%s)"

# # 受影响的行数

# r = cursor.executemany(sql,[('egon','sb'),('laoyao','BS')])

# #

# conn.commit()

# cursor.close()

# conn.close()

# 查

# conn = pymysql.connect(host="localhost",user='root',password='',database="db666")

# cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)

# sql = "select * from userinfo"

# cursor.execute(sql)

# cursor.scroll(1,mode='relative') # 相对当前位置移动

# cursor.scroll(2,mode='absolute') # 相对绝对位置移动

# result = cursor.fetchone()

# print(result)

# result = cursor.fetchone()

# print(result)

# result = cursor.fetchone()

# print(result)

# result = cursor.fetchall()

# print(result)

# result = cursor.fetchmany(4)

# print(result)

# cursor.close()

# conn.close()

# 新插入数据的自增ID: cursor.lastrowid

# import pymysql

# conn = pymysql.connect(host="localhost",user='root',password='',database="db3")

# cursor = conn.cursor()

# sql = "insert into userinfo(username,pwd) values('asdfasdf','')"

# cursor.execute(sql)

# conn.commit()

# print(cursor.lastrowid) #lastrowid最后一个自增id

# cursor.close()

# conn.close()

6、作业

作业：

参考表结构：

用户类型

用户信息

权限

用户类型&权限

功能：

# 登陆、注册、找回密码

# 用户管理

# 用户类型

# 权限管理

# 分配权限

特别的：程序仅一个可执行文件

讯享网

create database wuSir default character set utf8 collate utf8_general_ci;

use wuSir;

create table auth_info(

aid intnotnull auto_increment primary key,

auth_name varchar(32),

unique(auth_name)

)engine=innodb default charset=utf8;

create table user_info(

uid intnotnull auto_increment primary key,

name varchar(32),

passwd varchar(32),

sex ENUM("男","女")

)engine=innodb default charset=utf8;

create table user_auth(

id int,

auth_id int,

constraint auth_info foreign key(auth_id) references auth_info(aid),

constraint user_info foreign key(id) references user_info(uid)

)engine=innodb default charset=utf8;

insert into auth_info(auth_name) values("订单管理"),("用户管理"),("菜单管理"),("权限分配"),("Bug管理");

insert into user_info(name,passwd,sex) values("alex",123,"男"),("egon",123,"男");

insert into user_auth(id,auth_id) values(1,1),(2,1),(2,2),(2,3);

创建库表 SQL

importpymysql

user= input("please input name:").strip()

passwd= input("please input passwd:").strip()

conn= pymysql.connect(host="10.37.129.3",port=3306,user="egon",passwd="",db="wuSir",charset="utf8")

cursor= conn.cursor(cursor=pymysql.cursors.DictCursor)

sql= "select * from user_info where name=%s and passwd=%s"cursor.execute(sql,(user,passwd,))

result=cursor.fetchone()if result["name"] == user and result["passwd"] ==passwd:

uid= result["uid"]#print(uid)

sql = "select auth_name from auth_info where aid in (select auth_id from user_auth where id =%s)"cursor.execute(sql,(uid,))

result=cursor.fetchall()for i inresult:print(i["auth_name"])else:print("error")

cursor.close()

conn.close()

Python 代码

SQLAchemy

SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果。

安装：

pip3 install SQLAlchemy

SQLAlchemy本身无法操作数据库，其必须以来pymsql等第三方插件，Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作，如：

MySQL-Python

mysql+mysqldb://:@[:]/

pymysql

mysql+pymysql://:@/[?]

MySQL-Connector

mysql+mysqlconnector://:@[:]/

cx_Oracle

oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]

更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html

一、内部处理

使用 Engine/ConnectionPooling/Dialect 进行数据库操作，Engine使用ConnectionPooling连接数据库，然后再通过Dialect执行SQL语句。

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

# 执行SQL

# cur = engine.execute(

# "INSERT INTO hosts (host, color_id) VALUES ('1.1.1.22', 3)"

# )

# 新插入行自增ID

# cur.lastrowid

# 执行SQL

# cur = engine.execute(

# "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),]

# )

# 执行SQL

# cur = engine.execute(

# "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)",

# host='1.1.1.99', color_id=3

# )

# 执行SQL

# cur = engine.execute('select * from hosts')

# 获取第一行数据

# cur.fetchone()

# 获取第n行数据

# cur.fetchmany(3)

# 获取所有数据

# cur.fetchall()

二、ORM功能使用

使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象，对象转换成SQL，执行SQL。

1、创建表

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

Base = declarative_base()

# 创建单表

class Users(Base):

__tablename__ = 'users'

id = Column(Integer, primary_key=True)

name = Column(String(32))

extra = Column(String(16))

__table_args__ = (

UniqueConstraint('id', 'name', name='uix_id_name'),

Index('ix_id_name', 'name', 'extra'),

)

# 一对多

class Favor(Base):

__tablename__ = 'favor'

nid = Column(Integer, primary_key=True)

caption = Column(String(50), default='red', unique=True)

class Person(Base):

__tablename__ = 'person'

nid = Column(Integer, primary_key=True)

name = Column(String(32), index=True, nullable=True)

favor_id = Column(Integer, ForeignKey("favor.nid"))

# 多对多

class Group(Base):

__tablename__ = 'group'

id = Column(Integer, primary_key=True)

name = Column(String(64), unique=True, nullable=False)

port = Column(Integer, default=22)

class Server(Base):

__tablename__ = 'server'

id = Column(Integer, primary_key=True, autoincrement=True)

hostname = Column(String(64), unique=True, nullable=False)

class ServerToGroup(Base):

__tablename__ = 'servertogroup'

nid = Column(Integer, primary_key=True, autoincrement=True)

server_id = Column(Integer, ForeignKey('server.id'))

group_id = Column(Integer, ForeignKey('group.id'))

def init_db():

Base.metadata.create_all(engine)

def drop_db():

Base.metadata.drop_all(engine)

注：设置外检的另一种方式 ForeignKeyConstraint(['other_id'], ['othertable.other_id'])

2、操作表

表结构 + 数据库连接

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

Base = declarative_base()

# 创建单表

class Users(Base):

__tablename__ = 'users'

id = Column(Integer, primary_key=True)

name = Column(String(32))

extra = Column(String(16))

__table_args__ = (

UniqueConstraint('id', 'name', name='uix_id_name'),

Index('ix_id_name', 'name', 'extra'),

)

def __repr__(self):

return "%s-%s" %(self.id, self.name)

# 一对多

class Favor(Base):

__tablename__ = 'favor'

nid = Column(Integer, primary_key=True)

caption = Column(String(50), default='red', unique=True)

def __repr__(self):

return "%s-%s" %(self.nid, self.caption)

class Person(Base):

__tablename__ = 'person'

nid = Column(Integer, primary_key=True)

name = Column(String(32), index=True, nullable=True)

favor_id = Column(Integer, ForeignKey("favor.nid"))

# 与生成表结构无关，仅用于查询方便

favor = relationship("Favor", backref='pers')

# 多对多

class ServerToGroup(Base):

__tablename__ = 'servertogroup'

nid = Column(Integer, primary_key=True, autoincrement=True)

server_id = Column(Integer, ForeignKey('server.id'))

group_id = Column(Integer, ForeignKey('group.id'))

group = relationship("Group", backref='s2g')

server = relationship("Server", backref='s2g')

class Group(Base):

__tablename__ = 'group'

id = Column(Integer, primary_key=True)

name = Column(String(64), unique=True, nullable=False)

port = Column(Integer, default=22)

# group = relationship('Group',secondary=ServerToGroup,backref='host_list')

class Server(Base):

__tablename__ = 'server'

id = Column(Integer, primary_key=True, autoincrement=True)

hostname = Column(String(64), unique=True, nullable=False)

def init_db():

Base.metadata.create_all(engine)

def drop_db():

Base.metadata.drop_all(engine)

Session = sessionmaker(bind=engine)

session = Session()

增

obj = Users(name="alex0", extra='sb')

session.add(obj)

session.add_all([

Users(name="alex1", extra='sb'),

Users(name="alex2", extra='sb'),

])

session.commit()

删

session.query(Users).filter(Users.id > 2).delete()

session.commit()

改

session.query(Users).filter(Users.id > 2).update({"name" : "099"})

session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)

session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")

session.commit()

查

ret = session.query(Users).all()

ret = session.query(Users.name, Users.extra).all()

ret = session.query(Users).filter_by(name='alex').all()

ret = session.query(Users).filter_by(name='alex').first()

ret = session.query(Users).filter(text("id<:value and name=':name")).params(value=224,'>

ret = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()

其他

#　条件

ret = session.query(Users).filter_by(name='alex').all()

ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()

ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()

ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()

ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()

ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()

from sqlalchemy import and_, or_

ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()

ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()

ret = session.query(Users).filter(

or_(

Users.id < 2,

and_(Users.name == 'eric', Users.id > 3),

Users.extra != ""

)).all()

# 通配符

ret = session.query(Users).filter(Users.name.like('e%')).all()

ret = session.query(Users).filter(~Users.name.like('e%')).all()

# 限制

ret = session.query(Users)[1:2]

# 排序

ret = session.query(Users).order_by(Users.name.desc()).all()

ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()

# 分组

from sqlalchemy.sql import func

ret = session.query(Users).group_by(Users.extra).all()

ret = session.query(

func.max(Users.id),

func.sum(Users.id),

func.min(Users.id)).group_by(Users.name).all()

ret = session.query(

func.max(Users.id),

func.sum(Users.id),

func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()

# 连表

ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()

ret = session.query(Person).join(Favor).all()

ret = session.query(Person).join(Favor, isouter=True).all()

# 组合

q1 = session.query(Users.name).filter(Users.id > 2)

q2 = session.query(Favor.caption).filter(Favor.nid < 2)

ret = q1.union(q2).all()

q1 = session.query(Users.name).filter(Users.id > 2)

q2 = session.query(Favor.caption).filter(Favor.nid < 2)

ret = q1.union_all(q2).all()

示例：

1、查询语法

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

Base = declarative_base()

# 创建单表

class UserType(Base):

__tablename__ = 'usertype'

id = Column(Integer, primary_key=True, autoincrement=True)

title = Column(String(32), nullable=True, index=True)

class Users(Base):

__tablename__ = 'users'

id = Column(Integer, primary_key=True, autoincrement=True) #主键自增

name = Column(String(32), nullable=True) #不为空

email = Column(String(16), unique=True) #唯一

user_type_id = Column(Integer,ForeignKey("usertype.id")) #外键

__table_args__ = (

UniqueConstraint('name', 'email', name='uix_id_name'), #联合唯一索引

Index('ix_n_ex','name', 'email',),

)

engine = create_engine("mysql+pymysql://egon:@10.37.129.3:3306/day63?charset=utf8", max_overflow=5)

Session = sessionmaker(bind=engine)

session = Session()

# ret = session.query(Users)

#SELECT users.id AS users_id, users.name AS users_name, users.email AS users_email, users.user_type_id AS users_user_type_id FROM users

# ret = session.query(Users).all()

#[<__main__.users object at>, <__main__.users object at>, <__main__.users object at>]

# ret = session.query(Users.name, Users.email).all()

# [('alex', '163'), ('egon', '173'), ('wuSir', '183')]

# ret = session.query(Users).filter_by(name='alex').all()

# [<__main__.users object at>]

# ret = session.query(Users).filter_by(name='alex').first()

# <__main__.users object at>

#user_list = session.query(UserType.id,UserType.title).filter(UserType.id>=1).all()

# [(1, '普通用户'), (2, '黄金用户')]

session.commit()

session.close()

2、插入语法

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

Base = declarative_base()

# 创建单表

class UserType(Base):

__tablename__ = 'usertype'

id = Column(Integer, primary_key=True, autoincrement=True)

title = Column(String(32), nullable=True, index=True)

class Users(Base):

__tablename__ = 'users'

id = Column(Integer, primary_key=True, autoincrement=True) #主键自增

name = Column(String(32), nullable=True) #不为空

email = Column(String(16), unique=True) #唯一

user_type_id = Column(Integer,ForeignKey("usertype.id")) #外键

__table_args__ = (

UniqueConstraint('name', 'email', name='uix_id_name'), #联合唯一索引

Index('ix_n_ex','name', 'email',),

)

engine = create_engine("mysql+pymysql://egon:@10.37.129.3:3306/day63?charset=utf8", max_overflow=5)

Session = sessionmaker(bind=engine)

session = Session()

#方式一：

# obj = UserType(title="普通用户")

# obj1 = UserType(title="黄金用户")

# session.add(obj)

# session.add(obj1)

#方式二:

objs= [

Users(name="alex",email="163",user_type_id=1),

Users(name="egon",email="173",user_type_id=1),

Users(name="tom",email="183",user_type_id=2)

]

session.add_all(objs)

session.commit()

session.close()

3、删除修改语法

#删除

# session.query(Users).filter(Users.id>1).delete()

#修改

#session.query(Users).filter(Users.id > 2).update({"name" : "099"})

#session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)

#session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")

from sqlalchemy.ext.declarative importdeclarative_basefrom sqlalchemy importColumn, Integer, String, ForeignKey, UniqueConstraint, Index,CHAR,VARCHARfrom sqlalchemy.orm importsessionmaker, relationshipfrom sqlalchemy importcreate_engine#创建对象的基类:

Base =declarative_base()#创建单表

"""1 白金

2 黑金

obj.xx ==> [obj,obj...]"""

#创建表单usertype

classUserType(Base):#表的名字:

__tablename__ = 'usertype'

#表的结构:

id = Column(Integer, primary_key=True, autoincrement=True)

title= Column(VARCHAR(32), nullable=True, index=True)"""1 方少伟 1

2 成套 1

3 小白 2

# 正向

ut = relationship(backref='xx')

obj.ut ==> 1 白金"""

classUsers(Base):__tablename__ = 'users'id= Column(Integer, primary_key=True, autoincrement=True)

name= Column(VARCHAR(32), nullable=True, index=True)

email= Column(VARCHAR(16), unique=True)

user_type_id= Column(Integer,ForeignKey("usertype.id"))

user_type= relationship("UserType",backref='xxoo') #一对多:

#__table_args__ = (

#UniqueConstraint('id', 'name', name='uix_id_name'),

#Index('ix_n_ex','name', 'email',),

defcreate_db():

engine= create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5)#新增表

Base.metadata.create_all(engine)defdrop_db():

engine= create_engine("mysql+pymysql://root:@127.0.0.1:3306/s4day62db?charset=utf8", max_overflow=5)#删除表

Base.metadata.drop_all(engine)#初始化数据库连接:(create_engine()用来初始化数据库连接)

engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/db5?charset=utf8", max_overflow=5)#'数据库类型+数据库驱动名称://用户名:口令@机器地址:端口号/数据库名'#mysql使用的数据库，pymysql模板，root账户，root : 后加密码，mysql客户端未设置密码。db5为数据库，max_overflow代表最大连接数量

#新增表

Base.metadata.create_all(engine)#创建Session类型:

Session = sessionmaker(bind=engine)#创建session对象:

session =Session()#类 -> 表#对象 -> 行增加 # 创建新obj1对象#obj1 = UserType(title='普通用户') 添加到session:#session.add(obj1)

#objs =[#UserType(title='超级用户'),#UserType(title='白金用户'),#UserType(title='黑金用户'),#]#session.add_all(objs)

查 print(session.query(UserType)) 创建Query查询，调用one()返回一行，如果调用all()则返回所有行:#user_type_list = session.query(UserType).all() #session.query(UserType)相当于迭代器，不加 .all()的话，for循环结果也是一样的#for row in user_type_list:#print(row.id,row.title)

select UserType.id,UserType.title UserType where UserType.id > 2 #sql语句#user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id > 2) #使用框架sqlalchemy来实现，filter过滤#for row in user_type_list:#print(row.id,row.title)

#print(user_type_list) #打印结果：SELECT usertype.id AS usertype_id, usertype.title AS usertype_title FROM usertype WHERE usertype.id > %(id_1)s

#分组，排序，连表，通配符，子查询，limit，union,where,原生SQL#ret = session.query(Users, UserType)#select * from user,usertype;#

#ret = session.query(Users, UserType).filter(Users.usertype_id==UserType.id)#select * from user,usertype whre user.usertype_id = usertype.id

#result = session.query(Users).join(UserType)#print(result)

#result = session.query(Users).join(UserType,isouter=True)#print(result)

#sql语句用sqlalchemy框架实现：#1.#select * from b where id in (select id from tb2) #sql语句#sqlalchemy框架实现: ...

#2#select * from (select * from UserType where UserType.id > 0) as B #sql语句#sqlalchemy框架实现:#q1 = session.query(UserType).filter(UserType.id > 0).subquery() #subquery()子查询#print(q1)#result = session.query(q1).all()#print(result)

#3#select id ,(select * from users where users.user_type_id=usertype.id) from usertype; #sql语句,嵌套sql语句select * from users where users.user_type_id=usertype.id#sqlalchemy框架实现:#session.query(UserType,session.query(Users).filter(Users.id == 1).subquery()) #subquery()子查询的固定用法,有嵌套sql语句为子查询，需使用subquery()#session.query(UserType,Users)#result = session.query(UserType.id,session.query(Users).as_scalar()) #as_scalar() 相当于临时表的固定用法#print(result)#result = session.query(UserType.id,session.query(Users).filter(Users.user_type_id==UserType.id).as_scalar())#print(result)

#问题1. 获取用户信息以及与其关联的用户类型名称(FK,Relationship=>正向操作)#user_list = session.query(Users,UserType).join(UserType,isouter=True) #联表left ... join ...on... print(user_list)#for row in user_list:#print(row[0].id,row[0].name,row[0].email,row[0].user_type_id,row[1].title) # row[0] 为表Users，row[1]为表UserType

#user_list= session.query(Users.name,UserType.title) #不同表不可以直接获取，需要联表获取#print("user_list:",user_list) #SELECT users.name AS users_name, usertype.title AS usertype_title FROM users, usertype

#user_list = session.query(Users.name,UserType.title).join(UserType,isouter=True).all() #左联表#user_list = session.query(UserType.title,Users.name).join(Users,isouter=True).all() #换个位置后，就变成右联表#isouter=True代表左联表left ... join ...on...，不加isouter=True代表inner ... join ... on ...#print("user_list:",user_list)#for row in user_list:#print("row:",row) #打印结果是元组形式，所以row[0]与row.name，row[1]和row.title打印结果是一样的#print(row[0],row[1],row.name,row.title)

#user_list = session.query(Users)#for row in user_list:#print(row.name,row.id,row.user_type.title) #row.user_type.title，建表users时使用了user_type = relationship("UserType",backref='xxoo')--->xyp 1 超级用户 #row.user_type.title,表user和usertype建立了连接，user的行可以直接调用usertype的内容 xyp2 2 白金用户

#问题2. 获取用户类型

type_list =session.query(UserType)for row intype_list:print(row.id,row.title,session.query(Users).filter(Users.user_type_id ==row.id).all())#--->2 白金用户 [<__main__.users object at>]

#1 超级用户 [<__main__.users object at>]

#3 黑金用户[] #因为user表仅二行，所以usertype表的id就无法与Users第三行的user_type_id 匹配

#type_list = session.query(UserType)#for row in type_list:#print(row.id,row.title,row.xxoo) #建表users时使用了user_type = relationship("UserType",backref='xxoo')

#--->2 白金用户 [<__main__.users object at>]

#1 超级用户 [<__main__.users object at>]

#3 黑金用户 []

删除 session.query(UserType.id,UserType.title).filter(UserType.id > 2).delete() # 删除前需先查

修改修改前需先查#改变全部title列为"黑金"：#session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"title" : "黑金"})#改变UserType.id > 0的title列加字符串"x"，synchronize_session=False用在修改字符串固定用法#session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({UserType.title: UserType.title + "x"}, synchronize_session=False)#改变UserType.id > 0的title列，num列建表时未建，Users.num + 1，整型的计算。synchronize_session="evaluate" 用在修改整型固定用法#session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"num": Users.num + 1}, synchronize_session="evaluate")

#提交即保存到数据库:

session.commit()#关闭session:

session.close()

补充

更多功能参见文档，猛击这里下载PDF

python propresql mysql_Python操作MySQL：pymysql和SQLAlchemy

相关推荐