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="123456",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="123456",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','123123')"

# 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','123123')"

# 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
create database wuSir default character set utf8 collate utf8_general_ci;

use wuSir;

create table auth_info(

    aid int not null auto_increment primary key,

    auth_name varchar(32),

    unique(auth_name)

    )engine=innodb default charset=utf8;

create table user_info(

    uid int not null 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

import pymysql

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 in result:

        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://<user>:<password>@<host>[:<port>]/<dbname>

pymysql

    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]

MySQL-Connector

    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>

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, name='fred').order_by(User.id).all()

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:123456@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 0x1037620f0>, <__main__.Users object at 0x103762160>, <__main__.Users object at 0x1037621d0>]

# 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 0x103759198>]

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

#     <__main__.Users object at 0x103758240>

#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:123456@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 import declarative_base

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

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_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

class UserType(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

"""

class Users(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',),

    # )

def create_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)

def drop_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: ...

#

# 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)

#

# 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 in type_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 0x00000000039639E8>]

    #     1 超级用户 [<__main__.Users object at 0x0000000003963B00>]

    #     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 0x0000000003963DA0>]

    #     1 超级用户 [<__main__.Users object at 0x0000000003963F98>]

    #     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

最新文章

  1. wireshake抓包，飞秋发送信息，python
  2. Spring In Action ③
  3. windows下批量删除文件
  4. 位运算取第一个非0的位 r &amp; (~(r-1))
  5. jQuery给同一个元素两个点击事件
  6. codeigniter在nginx 下支持pathinfo和去除index.php的方法
  7. 移动端页面调试工具——UC浏览器开发者版
  8. python中的类简单讲解
  9. po 时不生效时， 不要用点方法
  10. [SAN4N学习笔记]使用SysTick精准延时
  11. A+B问题（java）
  12. Sql日期时间格式转换 备用
  13. hive内置函数大全
  14. codeforces 260 div2 A,B,C
  15. ES6关于Unicode的相关扩展
  16. 25个增强iOS应用程序性能的提示和技巧(0基础篇)
  17. Android开发支付集成——微信集成
  18. 消息中间件之一：RabbitMQ
  19. tensorflow (七) k-means
  20. Codeforces 311D Interval Cubing 数学 + 线段树 (看题解)

热门文章

  1. [python学习篇][廖雪峰][1]高级特性 ---迭代
  2. AtCoder Grand Contest 022
  3. tcpdump 进行抓包
  4. 九度oj 题目1171：C翻转
  5. 刷题总结：排序机械臂（石室中学oj）（splay）
  6. [JSOI2016] 最佳团队 (树形DP+01分数规划)
  7. spring的事务传播与隔离
  8. java面试题之@Autowired和@Resource的区别
  9. Java程序员最常犯的错误盘点之Top 10
  10. LeetCode OJ——Pascal&#39;s Triangle II