构造查询以对与给定A实例相关的所有B实例进行多对多过滤

问题描述

我想获取与特定TableA实例相关的所有TableB实例.这是一个多对多的关系.如何构造此查询?

I want to get all TableB instances that are related to a specific TableA instance. It is a many-to-many relationship. How do I construct this query?

class TableA(db.Model):
    __tablename__ = 'tableA'
    id = db.Column(db.Integer, primary_key=True)

class TableB(db.Model):
    __tablename__ = 'tableB'
    id = db.Column(db.Integer, primary_key=True)
    many_to_many = db.relationship(TableA, secondary='association_table')

association_table = db.Table('association',
    db.Column('tableA_id', db.Integer, db.ForeignKey(TableA.id)),
    db.Column('tableB_id', db.Integer, db.ForeignKey(TableB.id))
)

推荐答案

使用关系的 contains 方法以过滤与TableA项相关的TableB项.

Use the relationship's contains method to filter TableB items that are related to the TableA item.

session.query(TableB).filter(TableB.many_to_many.contains(eleA))

或使用 对关系执行更复杂的过滤器.

Or use any to perform more complex filters on the relationship.

# for example, all B's related to A's with id < 10
session.query(TableB).filter(TableB.many_to_many.any(TableA.id < 10))

或者如果要考虑大量数据的性能，请使用join和filter.

Or if performance over a very large set of data is a concern, use join and filter.

 session.query(TableB).join(TableB.many_to_many).filter(TableA.id == eleA.id)

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