SQLAlchemy: how to join tables and filter by != condition?

Question

SQLAlchemy for MySQL without foreign key, I've created these tables:

USER TABLE:
user_id
user_name

BLOCK TABLE:
user_id
blocked_user_id

POST TABLE:
post_id
post_user_id
post_content

COMMENT TABLE:
comment_id
comment_user_id
comment_content
post_id
post_user_id

I want to select post's comments and COMMENT.comment_user_id not in BLOCK.blocked_user_id , I've tried this, but result is empty:

comments = COMMENT.query.outerjoin(BLOCK, BLOCK.blocked_user_id == COMMENT.comment_user_id).filter(COMMENT.post_id == postid, COMMENT.post_user_id != current_user.user_id).all()

As alternative solution, I have to use two query steps, first step to select all blocked_users, second step to select post's comments filter by

COMMENT.comment_user_id.notin_(blocked_users)

Answer 1

assuming you can use session for sqlalchemy below query will return you the correct result as you taking left join on comment and block table

comments = session.query(COMMENT).outerjoin(BLOCK, COMMENT.user_id == BLOCK.user_id).filter(BLOCK.user_id == None).all()

so your original query will get something like below

comments = COMMENT.query.outerjoin(BLOCK, COMMENT.blocked_user_id == BLOCK.comment_user_id).filter(BLOCK.blocked_user_id==None).all()

Note : above query only filter all comments with userid which is not blocked table you can add your more filter conditions as per your requirement for other columns