SELECT tickets.id AS tickets_id, tickets.title AS tickets_title, companies.companyname AS companies_companyname, types.type_title AS types_type_title 
FROM tickets, companies, types

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String

Base = declarative_base()


class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    fullname = Column(String)

    def __repr__(self):
        return "<User(name='%s', fullname='%s', nickname='%s')>" % (
            self.name, self.fullname, self.nickname)

from base import User
target_metadata = User.metadata

(venv) [flopberry@localhost test]$ export PYTHONPATH=$PYTHONPATH:/home/flopberry/PycharmProjects/test/migrations/
(venv) [flopberry@localhost test]$ alembic revision -m "create user" --autogenerate --head head
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.autogenerate.compare] Detected added table 'users'
  Generating /home/flopberry/PycharmProjects/test/migrations/versions/9a50aafa1299_create_user.py ...  done

(venv) [flopberry@localhost test]$ alembic revision -m "create user" --autogenerate --head head
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
ERROR [alembic.util.messaging] Target database is not up to date.
  FAILED: Target database is not up to date.

users = db.session.query(UserData).all()

list_of_dicts = list_of_dicts(users)

for idx, user in enumerate(users):
   exists = db.session.query(AnotherTable).filter_by(user_id = user.user_id).scalar() is not None
   list_of_dicts[idx].update({"exists": exists})