mysql篇---ORM框架

Posted 2020-09-22 nayike

一.对于Python操作mysql主要使用两种方式：

• 原生模块 pymsql
• ORM框架 SQLAchemy

 

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

Pymysql(py2,py3)/MySQLDB(py2)

 

1.下载安装

pip3 install pymysql

 b.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()

View Code

 

 2.获取新创建数据自增ID

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

View Code

 

 3.获取查询数据

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()

View Code

 

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：

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()

View Code

 

二.ORM框架

#ORM框架有两类:
    1.DB first: 手动创建数据库以及表      -> ORM框架 -> 自动生成类
    2.code first： 手动创建类、和数据库   -> ORM框架 -> 以及表     (SQLAlchemy属于此)

功能：
　　　- 创建数据库表
        - 连接数据库（非SQLAlchemy, 可以：pymyql,mysqldb,....）
        - 类转换SQL语句  （SQLAlchemy：负责转换）
   
作用：
    1. 提供简单的规则
    2. 自动转换成SQL语句　　

ORM 原理：通过类和对象，转化为Sql语句，再借用第三方（如：Pymysql）去连接，去发送

 

 

三. SQLAlchemy

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

 

四.功能使用

#创建表的参照

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)

View Code

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

 

1.操作表

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column,Integer,String, VARCHAR,ForeignKey, UniqueConstraint,Index
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker,relationship

Base = declarative_base()

class UserType(Base):
    __tablename__ = \'usertype\'
    id = Column(Integer, primary_key=True, autoincrement=True)
    title = Column(VARCHAR(32), nullable=True, index=True)


class Users(Base):
    __tablename__ = \'users\'
    id = Column(Integer, primary_key=True,autoincrement=True)
    name = Column(VARCHAR(32),nullable=True,index=True)
    email = Column(String(16))
    user_type_id = Column(Integer,ForeignKey(\'usertype.id\'))

    user_type = relationship(\'UserType\',backref=\'xx\')


def create_db():
    engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/alchemy?charset=utf8", max_overflow=5)
    Base.metadata.create_all(engine)

def drop_db():
    engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/alchemy?charset=utf8", max_overflow=5)
    Base.metadata.drop_all(engine)


engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/alchemy?charset=utf8", max_overflow=5)
Session = sessionmaker(bind=engine)
session = Session()      #这里的session是 会话,连接的意思


#---创建表
# create_db()
# drop_db()

session.commit() #不要忘了 commit
session.close()

 

##---增加---
obj = UserType(title=\'普通用户\')
session.add(obj)

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))
user_type_list = session.query(UserType).all()
for row in user_type_list:
    print(row.id,row.title)


user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id > 2)
for row in user_type_list:
    print(row.id,row.title)

##----------删
session.query(UserType).filter(UserType.id > 0).delete()

##----------修改
session.query(UserType.id,UserType.title).filter(UserType.id > 1).update({"title" : "黑金"})
session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({UserType.title: UserType.title + "x"}, synchronize_session=False)

session.query(UserType.id,UserType.title).filter(UserType.id > 0).update({"num": Users.num + 100}, synchronize_session="evaluate") #没有添加此字段

增删改查

 

# 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)


#

# 1.
# select * from b where id in (select id from tb2)

# 2 select * from (select * from tb) as B
# q1 = session.query(UserType).filter(UserType.id > 0).subquery()
# result = session.query(q1).all()
# print(result)

# 3
# select
#   id ,
#   (select * from users where users.user_type_id=usertype.id)
# from usertype;

# session.query(UserType,session.query(Users).filter(Users.id == 1).subquery())
# session.query(UserType,Users)
# result = session.query(UserType.id,session.query(Users).as_scalar())
# 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)
# 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)

# user_list = session.query(Users.name,UserType.title).join(UserType,isouter=True).all()
# for row in user_list:
#     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)


# 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())

# type_list = session.query(UserType)
# for row in type_list:
#     print(row.id,row.title,row.xxoo)

其他一

#　条件
ret = session.query(Users).filter_by(name=\'tom\').all()
ret = session.query(Users).filter(Users.id > 1, Users.name == \'tom\').all()
ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == \'tom\').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=\'tom\'))).all()
from sqlalchemy import and_, or_
ret = session.query(Users).filter(and_(Users.id > 3, Users.name == \'tom\')).all()
ret = session.query(Users).filter(or_(Users.id < 2, Users.name == \'tom\')).all()
ret = session.query(Users).filter(
    or_(
        Users.id < 2,
        and_(Users.name == \'tom\', Users.id > 3),
        Users.extra != ""
    )).all()


# 通配符
ret = session.query(Users).filter(Users.name.like(\'t%\')).all()
ret = session.query(Users).filter(~Users.name.like(\'t%\')).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()

其他二

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

## relationship

 

 

 

有 relationship