Python操作MySQL：pymysql和SQLAlchemy
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
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