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python - Sqlalchemy 为父母过滤父子表

问题描述

我有一些我正在尝试搜索的模型，所以我希望显示返回所有父对象的结果，其中父名称为“foo”或子名称为“foo”。

我有一个查询：

parents = Session.query(Parent).\
            join(Child_s3).\
            filter(Parent.name.ilike("%foo%")).\
            filter(Child_s3.name.ilike("%foo%")).\
            order_by(asc(Product.name))

和模型：

class Parent(BaseSO):
    __tablename__ = 'parents'
    id = Column(Integer, primary_key=True)
    name = Column(Unicode(100), nullable=False, unique=True)
    colours = relationship('Child_s3', secondary=Parent_images, backref='Parentc')

class Child_s3(BaseSO):
    __tablename__ = 'children'
    id = Column(Integer, primary_key=True)
    name = Column(Unicode)

Parent_images = Table(
    'Parent_images', BaseSO.metadata,
    Column('parent_id', Integer, ForeignKey('parents.id')),
    Column('child_id', Integer, ForeignKey('children.id'))
)

我的查询显示了名为“foo”的父对象，但没有显示任何父对象，也有名为“foo”的子对象，任何人都可以帮助构建此查询以在两个表中搜索相应的父对象吗？

标签： pythonsqlalchemy

解决方案

此代码显示如何使用显式连接或子查询获取结果：

import sqlalchemy as sa
from sqlalchemy import orm
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


Parent_images = sa.Table(
    'Parent_images', Base.metadata,
    sa.Column('parent_id', sa.Integer, sa.ForeignKey('parents.id')),
    sa.Column('child_id', sa.Integer, sa.ForeignKey('children.id'))
)


class Parent(Base):
    __tablename__ = 'parents'
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.Unicode(100), nullable=False, unique=True)
    colours = orm.relationship('Child_s3', secondary=Parent_images, backref='parents')

    def __repr__(self):
        return 'Parent(name=%s)' % self.name

    __str__ = __repr__


class Child_s3(Base):
    __tablename__ = 'children'
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.Unicode)

    def __repr__(self):
        return 'Child_s3(name=%s)' % self.name

    __str__ = __repr__


if __name__ == '__main__':
    engine = sa.create_engine('sqlite:///')
    Base.metadata.drop_all(engine)
    Base.metadata.create_all(engine)
    Session = orm.sessionmaker(bind=engine)

    session = Session()
    for parent, child in [('boofoo', 'spam'), ('baz', 'foobar'), ('bar', 'quux')]:
        p1 = Parent(name=parent)
        session.add(p1)
        p1.colours.append(Child_s3(name=child))
    session.commit()

    print('Join')
    session = Session()
    q = (session.query(Parent)
                .join(Child_s3, Parent.colours)
                .filter(sa.or_(Parent.name.ilike('%foo%'),
                               Child_s3.name.ilike('%foo%'))))
    for p in q.all():
        print(p, p.colours)
    session.commit()
    print()

    print('Subquery')
    session = Session()
    q = (session.query(Parent)
                .filter(sa.or_(Parent.name.ilike('%foo%'),
                               Parent.colours.any(Child_s3.name.ilike('%foo%')))))
    for p in q.all():
        print(p, p.colours)
    session.commit()
    print()

连接查询

q = (session.query(Parent)
            .join(Child_s3, Parent.colours)
            .filter(sa.or_(Parent.name.ilike('%foo%'),
                           Child_s3.name.ilike('%foo%'))))

生成此 SQL

SELECT parents.id AS parents_id, parents.name AS parents_name 
FROM parents JOIN "Parent_images" AS "Parent_images_1" ON parents.id = "Parent_images_1".parent_id JOIN children ON children.id = "Parent_images_1".child_id 
WHERE lower(parents.name) LIKE lower(?) OR lower(children.name) LIKE lower(?)

子查询

q = (session.query(Parent)
            .filter(sa.or_(Parent.name.ilike('%foo%'),
                            Parent.colours.any(Child_s3.name.ilike('%foo%')))))

生成此 SQL：

SELECT parents.id AS parents_id, parents.name AS parents_name            
FROM parents                                                                                                                        
WHERE lower(parents.name) LIKE lower(?) OR (EXISTS (SELECT 1                                                                        
FROM "Parent_images", children                                                                                                      
WHERE parents.id = "Parent_images".parent_id AND children.id = "Parent_images".child_id AND lower(children.name) LIKE lower(?)))

该脚本从示例数据生成此输出：

Join
Parent(name=baz) [Child_s3(name=foobar)]
Parent(name=boofoo) [Child_s3(name=spam)]

Subquery
Parent(name=boofoo) [Child_s3(name=spam)]
Parent(name=baz) [Child_s3(name=foobar)]

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