python - 使用 SQLAlchemy 核心 API 过滤相关模型（使用 AIOPG）

Question

我正在尝试做一些我相当确定使用 AIOPG 很简单的事情，它可以使用 sqlalchemy 的核心 API。我的 SQL 不是很好，所以这就是我跌倒的地方。

楷模

class School(Base):
    __tablename__ = 'schools'

    id = Column(Integer, primary_key=True, nullable=False)


sa_school = School.__table__


class SubjectCategory(Base):
    __tablename__ = 'subject_categories'

    id = Column(Integer, primary_key=True, nullable=False)
    name = Column(String(63))


sa_subject_category = SubjectCategory.__table__


class Subject(Base):
    __tablename__ == 'subjects'

    id = Column(Integer, primary_key=True, nullable=False)
    name = Column(String(63))
    category = Column(Integer, ForeignKey('subject_categories.id'), nullable=False)


sa_subject = Subject.__table__


class SchoolSubject(Base):
    __tablename__ = 'school_subjects'

    id = Column(Integer, primary_key=True, nullable=False)
    school = Column(Integer, ForeignKey('schools.id'), nullable=False)
    subject = Column(Integer, ForeignKey('subjects.id'), nullable=False)


sa_school_subject = SchoolSubject.__table__

因此，我只是想获取所有schools具有特定subject_categoryID 的教学科目。

目前我有：

from sqlalchemy import select, join

school_c = sa_school.c
school_subj_c = sa_school_subject.c


async def get_schools(subject=None, subj_cat=None)
    query = select(
        [school_c.id, school_c.name]
    ).select_from(sa_school.join(sa_school_subject)
    if subj_cat:
        # Then I need to filter where a school_subj.subject.category == subj_cat
        pass
    elif subject:
        query = query.where(sa_school_subject.c.subject == subj)

    cur = await conn.execute(query)
    return [dict(b) async for b in cur]

Answer 1

经过一番折腾，我可以简单地做：

query = select(
    [school_c.id, school_c.name]
).select_from(sa_school.join(sa_school_subject.join(sa_subject)))