标签：root import date() use where bin back 创建对象 roo
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:
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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...]
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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
标签：root import date() use where bin back 创建对象 roo
原文地址：https://www.cnblogs.com/ExMan/p/9807144.html
