Python—sqlalchemy
2024-10-16 11:26:00
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。
#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:
'''
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...]
'''
1、使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 进行数据库操作。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey,select
metadata = MetaData() user = Table('pepole', metadata,
Column('id', Integer, primary_key=True),
Column('name', String(20)),
) color = Table('color', metadata,
Column('id', Integer, primary_key=True),
Column('name', String(20)),
)
engine = create_engine("mysql+mysqldb://root:123456@172.16.8.47:3306/test" ,max_overflow=5)
#metadata.create_all(engine)创建表 conn = engine.connect()
#--增
#sql = user.insert().values(id=3, name='lisi')
#conn.execute(sql)
#conn.close()
#--删
#sql = user.delete().where(user.c.id == 1)
#conn.execute(sql)
#conn.close()
#--改
#sql = user.update().where(user.c.name == 'zhangsan').values(name='lisi')
#conn.execute(sql)
#conn.close()
#--查
#sql = select([user, ])
#sql = select([user.c.id, ])
#sql = select([user.c.name, color.c.name]).where(user.c.id==color.c.id)#查找user和color表中id相等的name
#sql = select([user.c.name]).order_by(user.c.name) #result = conn.execute(sql)
#print result.fetchall()
2、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。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine engine = create_engine("mysql+mysqldb://root:123456@192.168.0.110:3306/test" ,max_overflow=5)#echo=True显示过程 Base = declarative_base() class Host(Base):
__tablename__ = 'hosts'
id = Column(Integer, primary_key=True)
name = Column(String(50)) # 寻找Base的所有子类,按照子类的结构在数据库中生成对应的数据表信息
Base.metadata.create_all(engine)
增、删、改、查
Session = sessionmaker(bind=engine)
session = Session()
#--------增
u = Host(id=2, name='zhansgan')
session.add(u)
session.add_all([
Host(id=3, name='lisi'),
Host(id=4, name='wangwu')
])
session.commit()
#--------删
session.query(Host).filter(Host.id > 2).delete()
session.commit()
#--------改
session.query(Host).filter(Host.id == 2).update({'name' : "wangwu"})
session.commit()
#--------查
result=session.query(Host).filter_by(id=2).first()#first()第一个 all()全部
print result offs=session.query(Host).offset(1).all()#从第4条数据开始
print(offs) ret = session.query(Host).order_by(Host.id).all()#排序
ret = session.query(Host).order_by(Host.id)[0:3]#找出前3条记录 print(ret) session.commit()
query = session.query(Host.name)
print query.all()
print query.limit(1).all() # 最多返回 1 条记录
print query.offset(1).all() # 从第 2 条记录开始返回
print query.order_by(Host.name).all() # 排序
print query.order_by(Host.name.desc()).all()
filter其他常用功能:
equals
query.filter(User.name == 'ed')
not equals
query.filter(User.name != 'ed')
LIKE:
query.filter(User.name.like('%ed%'))
IN:
query.filter(User.name.in_(['ed', 'wendy', 'jack']))#在列表内存在就找出
# works with query objects too:
query.filter(User.name.in_(
session.query(User.name).filter(User.name.like('%ed%'))
))#先找出符合%ed%的列表在判断是否在该列表内
NOT IN:
query.filter(~User.name.in_(['ed', 'wendy', 'jack']))
IS NULL:
query.filter(User.name == None)
# alternatively, if pep8/linters are a concern
query.filter(User.name.is_(None))
IS NOT NULL:
query.filter(User.name != None)
# alternatively, if pep8/linters are a concern
query.filter(User.name.isnot(None))
AND:
from sqlalchemy import and_ query.filter(and_(User.name == 'ed', User.fullname == 'Ed Jones'))
OR:
from sqlalchemy import or_
query.filter(or_(User.name == 'ed', User.name == 'wendy'))
外键关联
一对多的关联引用parent.relationship()
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String(50))
group_id=Column(Integer,ForeignKey("group.id"))#关联
group=relationship("Group",backref="group_list")#可以通过group获取Group表里的数据,backref:反向关联 class Group(Base):
__tablename__ = 'group'
id = Column(Integer, primary_key=True)
name = Column(String(50))
#在表Group插入两个组
g1=Group(name="g1")
g2=Group(name="g2")
session.add_all([g1,g2])
session.commit()
#插入一个用户
g1=session.query(Group).filter(Group.name=="g1").first()
u = User(id=1, name='zhangsan',group_id=g1.id)
session.add(u) #可以通过User表查看zhangsan在Group表里对应的组
h=session.query(User).filter(User.name=="zhangsan").first()
print(h.group.name)
relationship()中的backref(反向关联)
#查看g1组下有几个用户关联
gg=session.query(Group).filter(Group.name=="g1").first()
print(gg.group_list)
join查询
INNER JOIN:
aa=session.query(User).join(User.group).all()
print(aa) aa=session.query(User).join(User.group).filter(Group.name=="g1").all()#加条件
print(aa)
多对多关联查询(需创建一个中间表)
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String,ForeignKey,Table
from sqlalchemy.orm import sessionmaker,relationship
from sqlalchemy import create_engine engine = create_engine("mysql+mysqldb://root:123456@172.16.8.47:3306/test" ,max_overflow=5)#echo=True显示过程
Base = declarative_base() #创建中间表,关联另外两个表
HostGroup = Table("Host_Group",Base.metadata,
Column("host_id",ForeignKey("host.id"),primary_key=True),
Column("group_id",ForeignKey("group.id"),primary_key=True),
) class Host(Base):
__tablename__ = 'host'
id = Column(Integer, primary_key=True)
name = Column(String(50))
#group_id=Column(Integer,ForeignKey("group.id")) group=relationship("Group",
secondary=HostGroup,#指定中间表的实例
backref="group_list")
def __repr__(self):
return "id:%s,name:%s"%(self.id,self.name) class Group(Base):
__tablename__ = 'group'
id = Column(Integer, primary_key=True)
name = Column(String(50),unique=True,nullable=False) def __repr__(self):
return "id:%s,name:%s"%(self.id,self.name) # 寻找Base的所有子类,按照子类的结构在数据库中生成对应的数据表信息
Base.metadata.create_all(engine)
创建组和主机
Session = sessionmaker(bind=engine)
session = Session() #创建组
g1 = Group(name="g1")
g2 = Group(name="g2")
g3 = Group(name="g3")
session.add_all([g1,g2,g3]) #创建主机
h1 = Host(name="172.0.0.1")
h2 = Host(name="172.0.0.2")
h3 = Host(name="172.0.0.3")
session.add_all([h1,h2,h3])
进行关联
groups = session.query(Group).all()#找出所有组 h1=session.query(Host).filter(Host.name=="172.0.0.1").first()#找出h1 h2=session.query(Host).filter(Host.name=="172.0.0.2").first()#找出h2 h1.group=groups#h1关联3个组
h2.group=groups[1:-1]#h2关联两个组
查询
g1=session.query(Group).filter(Group.name=="g1").first()
h2=session.query(Host).filter(Host.name=="172.0.0.1").first() print(g1.group_list)#查看g1组下有哪些主机
print(h2.group)#查看172.0.0.1属于哪些组
最新文章
- nginx 添加nginx-http-concat模块
- C#正则表达式判断输入日期格式是否正确
- Java算法-选择排序
- 【转】阿里2015校招面试回忆(成功拿到offer)
- nand flash,nor flash,spi flash,片上RAM,片外RAM
- 移植ok6410
- php数组去重复代码
- .NET 使用 MySql.Data.dll 动态库操作MySql的帮助类--MySqlHelper
- java战斗系列-战斗MAVENPW结构
- Spring.Net+Nhibernate+Asp.Net Mvc 框架
- (cljs/run-at (JSVM. :all) ";一起实现柯里化";)
- Servlet的理解
- Apache Commons介绍(转载)
- java获得上下周及本周日期
- BZOJ4122 : [Baltic2015]File paths
- s4-2 ALOHA 协议
- (原)PyTorch中使用指定的GPU
- 『PyTorch』第十四弹_torch.nn.Module类属性
- linux下判断文件和目录是否存在
- 恶意程序入侵 dbuspm-session 发现了新的方法制这种恶意程序