Custom SQLAlchemy query not returning the expected results when using subquery
I'm a bit lost with I'm working on a personal project and I'm working with SQLAlchemy in a Flask application, and I'm trying to create a complex query that involves a subquery. My goal is to fetch users along with their latest activity timestamps from the database, but I'm getting unexpected results. Here's a simplified version of my models: ```python from sqlalchemy import Column, Integer, String, DateTime, ForeignKey from sqlalchemy.orm import relationship from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String) activities = relationship('Activity', back_populates='user') class Activity(Base): __tablename__ = 'activities' id = Column(Integer, primary_key=True) user_id = Column(Integer, ForeignKey('users.id')) timestamp = Column(DateTime) user = relationship('User', back_populates='activities') ``` I wrote a query that attempts to fetch each user along with their latest activity timestamp: ```python from sqlalchemy.orm import aliased from sqlalchemy import select, func latest_activity = aliased(Activity) stmt = (select(User, func.max(latest_activity.timestamp).label('latest_activity')) .join(latest_activity, User.id == latest_activity.user_id) .group_by(User.id)) result = session.execute(stmt).all() ``` However, instead of getting a list of users along with their latest activity timestamps, I'm receiving a list of users but the `latest_activity` field is always `None`. I've confirmed that there are activities in the database for these users, but it seems my join isn't working as intended. I’ve also tried changing the join condition and the way I handle the subquery, but nothing seems to resolve the scenario. I validated that the relationships are correctly set up and the data exists, yet the scenario continues. I’m using SQLAlchemy 1.4.23 and Flask 2.0.2. Any suggestions on what might be going wrong or how to approach this question? Thanks in advance! This is part of a larger web app I'm building.