map Comment like this: from sqlalchemy.orm import query_expression
class Comment(Base): __tablename__ = 'comment' id = Column(Integer, primary_key=True) news_id = Column(Integer, ForeignKey(News.id)) is_read = query_expression() then you need to use options in your query to link the join to your subquery, as well as the is_read expression, to that object: from sqlalchemy.orm import contains_eager comment_read_query = ( session.query(CommentRead).filter( CommentRead.comment_id == Comment.id, CommentRead.user_id == 1, # Interested in reads by specific user ).exists().label('is_read') ) comment_query = session.query(Comment, comment_read_query).subquery() news = session.query(News).outerjoin(comment_query).options( contains_eager(News.comments, alias=comment_query).with_expression( Comment.is_read, comment_query.c.is_read) ).all() On Fri, May 25, 2018 at 11:28 AM, Marat Sharafutdinov <deca...@gmail.com> wrote: > The news has comments, the comments have readings by users. > I need to receive all the news with comments and readings of these comments > by a specific user. > The query is ok, but I can't get the value of the column `is_read` as an > attribute of the comment object. > > -- > SQLAlchemy - > The Python SQL Toolkit and Object Relational Mapper > > http://www.sqlalchemy.org/ > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > --- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at https://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.