[英]SQL Alchemy Strange behaviour Join Multiple Columns from same table
I'm trying to perform a query that involves joining two columns from the same column. 我正在尝试执行一个查询,该查询涉及将同一列中的两个列联接在一起。
These are my models: 这些是我的模型:
class Match(Base):
__tablename__ = 'matches'
id = Column(Integer, primary_key=True)
date = Column(Date, nullable=False)
time = Column(Time, nullable=True)
league_id = Column(ForeignKey('leagues.id'), nullable=False, index=True)
league = relationship('League', backref='matches')
type = Column(enums.matches_types)
home_id = Column(ForeignKey('teams.id'), nullable=False, index=True)
home = relationship('Team', foreign_keys=[home_id], backref='home_matches')
away_id = Column(ForeignKey('teams.id'), nullable=False, index=True)
away = relationship('Team', foreign_keys=[away_id], backref='away_matches')
class Team(Base):
__tablename__ = 'teams'
id = Column(Integer, primary_key=True)
name = Column(String, nullable=False)
country_id = Column(ForeignKey('countries.id'), nullable=False, index=True)
country = relationship('Country', backref='teams')
This is what I wrote in SQLAlchemy: 这是我在SQLAlchemy中写的:
self.db_match = Session.query(Match).join(home, Match.home).options(contains_eager(Match.home)
).join(away, Match.away).options(contains_eager(Match.away)
).join(Match.b_reference).options(contains_eager(Match.b_reference)
).filter(home.name == self.match['home']['name']
).filter(away.name == self.match['away']['name']
).filter(Match.date == self.match['date'])
The translation that SQLAlchemy does to pure SQL is the following: SQLAlchemy对纯SQL的转换如下:
SELECT teams_1.name, teams_2.name, matches.id, matches_b_reference_codes.code
FROM teams, matches JOIN teams AS teams_1 ON teams_1.id = matches.home_id
JOIN teams AS teams_2 ON teams_2.id = matches.away_id
JOIN matches_b_reference_codes ON matches.id = matches_b_reference_codes.match_id
WHERE teams_1.name = 'Portland Trail Blazers' AND teams_2.name = 'Miami Heat' AND matches.date = '2011-01-09';
But this is what I need: 但这是我需要的:
SELECT teams_1.name, teams_2.name, matches.id, matches_b_reference_codes.code
**FROM matches JOIN teams AS teams_1 ON teams_1.id = matches.home_id**
JOIN teams AS teams_2 ON teams_2.id = matches.away_id
JOIN matches_b_reference_codes ON matches.id = matches_b_reference_codes.match_id
WHERE teams_1.name = 'Portland Trail Blazers' AND teams_2.name = 'Miami Heat' AND matches.date = '2011-01-09';
You are using contains_eager
incorrectly. 您使用的
contains_eager
错误。 You need to specify the alias
parameter when you're joining to an alias: 加入
alias
时,需要指定alias
参数:
home = aliased(Team)
away = aliased(Away)
Session.query(Match).join(home, Match.home) \
.options(contains_eager(Match.home, alias=home)) \
.join(away, Match.away) \
.options(contains_eager(Match.away, alias=away)) \
... \
.filter(...)
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