Python 如何定义SQLAlchemy中的反向多态性？桌子_Python_Python 3.x_Sqlalchemy

Python 如何定义SQLAlchemy中的反向多态性？桌子

python python-3.x sqlalchemy

Python 如何定义SQLAlchemy中的反向多态性？桌子,python,python-3.x,sqlalchemy,Python,Python 3.x,Sqlalchemy,家长： id | child_type | child_id --- | ---------- |-------- 1 | Student | 5 7 | Student | 8 9 | Employee | 3 15 | Employee | 8 29 | Employee | 12 id | name --- | ---------- 1 | Jerry .. | ... 5 | Alex 8 | Tom id | name -

家长：

id  | child_type | child_id
--- | ---------- |--------
1   | Student    | 5
7   | Student    | 8
9   | Employee   | 3
15  | Employee   | 8
29  | Employee   | 12

id  | name
--- | ----------
1   | Jerry
..  | ...
5   | Alex
8   | Tom

id  | name
--- | ----------
3   | John
..  | ...
8   | Mike
12  | Susan

from sqlalchemy.ext.declarative import declarative_base, AbstractConcreteBase
from sqlalchemy.schema import Column, ForeignKey
from sqlalchemy.sql.sqltypes import Integer, String

Base = declarative_base()


class Parent(Base):
    __tablename__ = 'parents'
    id = Column(Integer, pirmary_key=True)
    child_type = Column(String)
    child_id = Column(Integer)
    child = relationship('Child', uselist=False)


class Child(AbstractConcreteBase, Base):
    name = Column(String)


class Student(Child):
    __tablename__ = 'students'
    __mapper_args__ = {
        'polymorphic_identity': 'Student',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)


class Employee(Child):
    __tablename__ = 'employees'
    __mapper_args__ = {
        'polymorphic_identity': 'Employee',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from models import Parent

if __name__ == '__main__':
    engine = create_engine('mysql~~', encoding='utf-8')
    session = sessionmaker(bind=engine)()

    parent_success_1 = session.query(Parent).get(1)  # <Parent(id=1, child_type='Student', child_id=5)>
    assert parent_success_1.child.name == 'Alex'     # success

    parent_success_2 = session.query(Parent).get(15) # <Parent(id=15, child_type='Employee', child_id=8)>
    assert parent_success_2.child.name == 'Mike'     # success

    parent_failure = session.query(Parent).get(7)    # <Parent(id=7, child_type='Student', child_id=8)>
    assert parent_failure.child.name == 'Tom'        # failed
    # sqlalchemy.orm.exc.MultipleResultsFound: Multiple rows were found for one()

学生：

id  | child_type | child_id
--- | ---------- |--------
1   | Student    | 5
7   | Student    | 8
9   | Employee   | 3
15  | Employee   | 8
29  | Employee   | 12

id  | name
--- | ----------
1   | Jerry
..  | ...
5   | Alex
8   | Tom

id  | name
--- | ----------
3   | John
..  | ...
8   | Mike
12  | Susan

from sqlalchemy.ext.declarative import declarative_base, AbstractConcreteBase
from sqlalchemy.schema import Column, ForeignKey
from sqlalchemy.sql.sqltypes import Integer, String

Base = declarative_base()


class Parent(Base):
    __tablename__ = 'parents'
    id = Column(Integer, pirmary_key=True)
    child_type = Column(String)
    child_id = Column(Integer)
    child = relationship('Child', uselist=False)


class Child(AbstractConcreteBase, Base):
    name = Column(String)


class Student(Child):
    __tablename__ = 'students'
    __mapper_args__ = {
        'polymorphic_identity': 'Student',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)


class Employee(Child):
    __tablename__ = 'employees'
    __mapper_args__ = {
        'polymorphic_identity': 'Employee',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from models import Parent

if __name__ == '__main__':
    engine = create_engine('mysql~~', encoding='utf-8')
    session = sessionmaker(bind=engine)()

    parent_success_1 = session.query(Parent).get(1)  # <Parent(id=1, child_type='Student', child_id=5)>
    assert parent_success_1.child.name == 'Alex'     # success

    parent_success_2 = session.query(Parent).get(15) # <Parent(id=15, child_type='Employee', child_id=8)>
    assert parent_success_2.child.name == 'Mike'     # success

    parent_failure = session.query(Parent).get(7)    # <Parent(id=7, child_type='Student', child_id=8)>
    assert parent_failure.child.name == 'Tom'        # failed
    # sqlalchemy.orm.exc.MultipleResultsFound: Multiple rows were found for one()

员工：

id  | child_type | child_id
--- | ---------- |--------
1   | Student    | 5
7   | Student    | 8
9   | Employee   | 3
15  | Employee   | 8
29  | Employee   | 12

id  | name
--- | ----------
1   | Jerry
..  | ...
5   | Alex
8   | Tom

id  | name
--- | ----------
3   | John
..  | ...
8   | Mike
12  | Susan

from sqlalchemy.ext.declarative import declarative_base, AbstractConcreteBase
from sqlalchemy.schema import Column, ForeignKey
from sqlalchemy.sql.sqltypes import Integer, String

Base = declarative_base()


class Parent(Base):
    __tablename__ = 'parents'
    id = Column(Integer, pirmary_key=True)
    child_type = Column(String)
    child_id = Column(Integer)
    child = relationship('Child', uselist=False)


class Child(AbstractConcreteBase, Base):
    name = Column(String)


class Student(Child):
    __tablename__ = 'students'
    __mapper_args__ = {
        'polymorphic_identity': 'Student',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)


class Employee(Child):
    __tablename__ = 'employees'
    __mapper_args__ = {
        'polymorphic_identity': 'Employee',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from models import Parent

if __name__ == '__main__':
    engine = create_engine('mysql~~', encoding='utf-8')
    session = sessionmaker(bind=engine)()

    parent_success_1 = session.query(Parent).get(1)  # <Parent(id=1, child_type='Student', child_id=5)>
    assert parent_success_1.child.name == 'Alex'     # success

    parent_success_2 = session.query(Parent).get(15) # <Parent(id=15, child_type='Employee', child_id=8)>
    assert parent_success_2.child.name == 'Mike'     # success

    parent_failure = session.query(Parent).get(7)    # <Parent(id=7, child_type='Student', child_id=8)>
    assert parent_failure.child.name == 'Tom'        # failed
    # sqlalchemy.orm.exc.MultipleResultsFound: Multiple rows were found for one()

文件夹 型号.py：

id  | child_type | child_id
--- | ---------- |--------
1   | Student    | 5
7   | Student    | 8
9   | Employee   | 3
15  | Employee   | 8
29  | Employee   | 12

id  | name
--- | ----------
1   | Jerry
..  | ...
5   | Alex
8   | Tom

id  | name
--- | ----------
3   | John
..  | ...
8   | Mike
12  | Susan

from sqlalchemy.ext.declarative import declarative_base, AbstractConcreteBase
from sqlalchemy.schema import Column, ForeignKey
from sqlalchemy.sql.sqltypes import Integer, String

Base = declarative_base()


class Parent(Base):
    __tablename__ = 'parents'
    id = Column(Integer, pirmary_key=True)
    child_type = Column(String)
    child_id = Column(Integer)
    child = relationship('Child', uselist=False)


class Child(AbstractConcreteBase, Base):
    name = Column(String)


class Student(Child):
    __tablename__ = 'students'
    __mapper_args__ = {
        'polymorphic_identity': 'Student',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)


class Employee(Child):
    __tablename__ = 'employees'
    __mapper_args__ = {
        'polymorphic_identity': 'Employee',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from models import Parent

if __name__ == '__main__':
    engine = create_engine('mysql~~', encoding='utf-8')
    session = sessionmaker(bind=engine)()

    parent_success_1 = session.query(Parent).get(1)  # <Parent(id=1, child_type='Student', child_id=5)>
    assert parent_success_1.child.name == 'Alex'     # success

    parent_success_2 = session.query(Parent).get(15) # <Parent(id=15, child_type='Employee', child_id=8)>
    assert parent_success_2.child.name == 'Mike'     # success

    parent_failure = session.query(Parent).get(7)    # <Parent(id=7, child_type='Student', child_id=8)>
    assert parent_failure.child.name == 'Tom'        # failed
    # sqlalchemy.orm.exc.MultipleResultsFound: Multiple rows were found for one()

main.py：

id  | child_type | child_id
--- | ---------- |--------
1   | Student    | 5
7   | Student    | 8
9   | Employee   | 3
15  | Employee   | 8
29  | Employee   | 12

id  | name
--- | ----------
1   | Jerry
..  | ...
5   | Alex
8   | Tom

id  | name
--- | ----------
3   | John
..  | ...
8   | Mike
12  | Susan

from sqlalchemy.ext.declarative import declarative_base, AbstractConcreteBase
from sqlalchemy.schema import Column, ForeignKey
from sqlalchemy.sql.sqltypes import Integer, String

Base = declarative_base()


class Parent(Base):
    __tablename__ = 'parents'
    id = Column(Integer, pirmary_key=True)
    child_type = Column(String)
    child_id = Column(Integer)
    child = relationship('Child', uselist=False)


class Child(AbstractConcreteBase, Base):
    name = Column(String)


class Student(Child):
    __tablename__ = 'students'
    __mapper_args__ = {
        'polymorphic_identity': 'Student',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)


class Employee(Child):
    __tablename__ = 'employees'
    __mapper_args__ = {
        'polymorphic_identity': 'Employee',
        'concrete': True
    }
    id = Column(Integer, ForeignKey(Parent.child_id), primary_key=True)

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from models import Parent

if __name__ == '__main__':
    engine = create_engine('mysql~~', encoding='utf-8')
    session = sessionmaker(bind=engine)()

    parent_success_1 = session.query(Parent).get(1)  # <Parent(id=1, child_type='Student', child_id=5)>
    assert parent_success_1.child.name == 'Alex'     # success

    parent_success_2 = session.query(Parent).get(15) # <Parent(id=15, child_type='Employee', child_id=8)>
    assert parent_success_2.child.name == 'Mike'     # success

    parent_failure = session.query(Parent).get(7)    # <Parent(id=7, child_type='Student', child_id=8)>
    assert parent_failure.child.name == 'Tom'        # failed
    # sqlalchemy.orm.exc.MultipleResultsFound: Multiple rows were found for one()

parent\u失败。child

[<Student(id=8, name='Tom')>, <Employee(id=8, name='Mike')>]

[，]

如何将

polymorphic\u on

设置为父级的child\u type列以使用它？

这在文档中讨论如下。我想你正在寻找的方法是。@univerio谢谢！