我的SQLAlchemy结构如下
papers2authors_table = Table('papers2authors', Base.metadata,
Column('paper_id', Integer, ForeignKey('papers.id')),
Column('author_id', Integer, ForeignKey('authors.id'))
)
class Paper(Base):
__tablename__ = "papers"
id = Column(Integer, primary_key=True)
title = Column(String)
handle = Column(String)
authors = relationship("Author",
secondary="papers2authors",
backref="papers")
class Author(Base):
__tablename__ = "authors"
id = Column(Integer, primary_key=True)
name = Column(String, unique=True)
code = Column(String, unique=True)
我想问两件事:
我用func.count()
和count()
尝试了许多选项,但它们返回的结果毫无意义。如何用SQLAlchemy的方式完成这两件事?
我所做的
db.s.query(func.count(core.Paper.id)).group_by(core.Author.id).first()
=sqlalchemy.exc.OperationalError: (OperationalError) no such column: authors.id
db.s.query(func.count(core.Author.papers)).group_by(core.Author.id).first()
=(128100)
,这不是我所期望的db.s.query(core.Author.papers).group_by(core.Author.id).count().first()
=AttributeError: 'int' object has no attribute 'first'
找到了解决方案:
db.s.query(core.Paper.title, func.count(core.Author.id)).join(core.Paper.authors).group_by(core.Paper.id).all()
db.s.query(core.Author.name, func.count(core.Author.id)).join(core.Author.papers).group_by(core.Author.id).all()
相关:http://docs.sqlalchemy.org/en/rel_0_9/orm/query.html#sqlalchemy.orm.query.Query.having
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