Python 使用sqlalchemy筛选父级的多个关系
假设我有以下三个类来描述一个音乐收藏:Python 使用sqlalchemy筛选父级的多个关系,python,join,sqlalchemy,Python,Join,Sqlalchemy,假设我有以下三个类来描述一个音乐收藏: from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint from sqlalchemy import Table from sqlalchemy.orm import relationship from sqlalchemy.ext.declarative import declarative_base TRACK_NAME_LEN = 64 ALBUM_
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint
from sqlalchemy import Table
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base
TRACK_NAME_LEN = 64
ALBUM_NAME_LEN = 64
TAG_NAME_LEN = 64
URL_LEN = 255
Base = declarative_base()
class Track(Base):
__tablename__ = 'tracks'
id = Column(Integer, primary_key=True)
name = Column(String(TRACK_NAME_LEN), nullable=False)
# many -> one
album_id = Column(Integer, ForeignKey('albums.id'), nullable=True)
album = relationship('Album', back_populates='tracks')
# Auxiliary table for many <--> many relationship
album_tag = Table('album_tag', Base.metadata,
Column('album_id', Integer, ForeignKey('albums.id')),
Column('tag_id', Integer, ForeignKey('tags.id')))
class Album(Base):
__tablename__ = 'albums'
id = Column(Integer, primary_key=True)
name = Column(String(ALBUM_NAME_LEN), nullable=False)
# one -> many
tracks = relationship('Track', back_populates='album')
# many -> many
tags = relationship(
'Tag',
secondary=album_tag,
back_populates='albums')
class Tag(Base):
__tablename__ = 'tags'
id = Column(Integer, primary_key=True)
name = Column(String(TAG_NAME_LEN), nullable=False, unique=True)
# many -> many
albums = relationship(
'Album',
secondary=album_tag,
back_populates='tags')
还有许多其他失败的尝试。
我们如何做到这一点?这是可行的:
session.query(Track).filter(Track.album.has(Album.tags.any(name='tango'))).all()
session.query(Track).filter(Track.album.has(Album.tags.any(name='tango'))).all()