Database url规则： dialect+driver://username:password@host:port/database

　　　　echo: True表示cmd窗口显示出对应的SQL 脚本信息

1 from sqlalchemy import create_engine
2 
3 # Database url: dialect+driver://username:password@host:port/database
4 # eq: mysql+pymysql://purk:max123@local/test
5 # 在内存中创建一个sqllite
6 # engine = create_engine(‘sqlite:///:memory:‘, echo=True)
7 # F:/test.db 如果test.db不存在，则创建一个。
8 engine = create_engine(‘sqlite:///F:/test.db‘, echo=True)

二、create mapping class

 1 from sqlalchemy import Column, Integer, String, Table
 2 from sqlalchemy.ext.declarative import declarative_base
 3 
 4 Base = declarative_base()
 5 
 6 
 7 class Person(Base):
 8     __tablename__ = ‘person‘
 9 
10     id = Column(Integer, primary_key=True)
11     name = Column(String(50))
12 
13 class User(Base):
14     __tablename__=‘user‘
15 
16     id = Column(Integer, primary_key=True)
17     name = Column(String(50))

1 >>> Person.__table__
2 Table(‘person‘, MetaData(bind=None), Column(‘id‘, Integer(), table=<person>, primary_key=True, nullable=False), Column(‘name‘, String(length=50), table=<person>), schema=None)
3 
4 >>> Person.metadata is User.metadata
5 True
6 
7 >>> Person.metadata is Base.metadata
8 True

 传统的mapper configuration 就不介绍了，因为不直观，而且代码量还长，下面只贴出官网的例子

 1 from sqlalchemy import Table, MetaData, Column, Integer, String, ForeignKey
 2 from sqlalchemy.orm import mapper
 3 metadata = MetaData()
 4 user = Table(‘user‘, metadata,
 5              Column(‘id‘, Integer, primary_key=True),
 6              Column(‘name‘, String(50)),
 7              Column(‘fullname‘, String(50)),
 8              Column(‘password‘, String(12))
 9              )
10 
11 
12 class User(object):
13 
14 
15 def __init__(self, name, fullname, password):
16 self.name = name
17 self.fullname = fullname
18 self.password = password
19 mapper(User, user)

三、Column

　　1. DataType

　　　　1) Integer

　　　　　　　 id = Column(Integer)

　　　　2) String

　　　　　　　 name = Column(String(50))

 　　　  3) Boolean

                      gender = Column(Boolean)

1 person = Person(name=‘purk‘, gender=0)
2 person1 = Person(name=‘purk1‘, gender=11)
3 person2 = Person(name=‘purk2‘, gender=-1)
4 # try:
5 #     person3 = Person(name=‘purk3‘, gender=‘123‘)
6 # except Exception as e:
7 #     print(‘boolean类型在数据库中对应的smartint或boolean类型，输入字符串是不对的‘)
8 db.add_all([person, person1, person2])
9 db.commit()

 结果如下

1 person_1 = db.query(Person).filter(Person.name == ‘purk‘).first()
2 person_2 = db.query(Person).filter(Person.name == ‘purk1‘).first()
3 person_3 = db.query(Person).filter(Person.name == ‘purk2‘).first()
4 print(person_1.gender)
5 print(person_2.gender)
6 print(person_3.gender)

查询 结果如下，满足boolean类型的一贯判断，非0即1.

　　　　　　4) Date  -> datetime.date()

                  5) DateTime -> datetime.datetime()

　　　　　　6) Enum

　　　　　　　　　　level_list = (‘low‘, ‘medium‘, ‘high‘)

　　　　　　　　　　level = Column(Enum(*level_list))

1 person = Person(name=‘purk‘, gender=True, level=‘123‘)
2 person1 = Person(name=‘purk1‘, gender=False, level=0)
3 person2 = Person(name=‘purk2‘, gender=False, level=1)
4 person3 = Person(name=‘purk3‘, gender=False, level=4)
5 person4 = Person(name=‘purk4‘, gender=-1, level=‘medium‘)

 Enum的index是从1开始的，越界的或者值不在枚举列中的都保存为null了

sqlalchemy - day1

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