如何在sqlalchemy ORM中表达此查询？

Question

Here is my SQL query:

select survey_spec.survey_spec_id, cr.login as created_by, installed_at, req.login as requested_by, role
from survey_spec
        join (select survey_spec_id, role, max(installed_at) as installed_at from survey_installation_history group by 1, 2) latest using (survey_spec_id)
        left join survey_installation_history using (survey_spec_id, role, installed_at)
        left join users cr on created_by = cr.user_id
        left join users req on requested_by = req.user_id
where survey_id = :survey_id
order by created_at desc, installed_at desc

I have ORM entities for survey_spec , survey_installation_history , and users , and survey_spec.installations is a relationship to survey_installation_history using survey_spec_id as the key.

Answer 1

Do you have the example output of what you have got so far? ie the output of:

print survey_spec.query.filter(survey_spec.survey_id==survey_id).options(
         eagerload(...))

If you just want to load up your entities, you could bypass the SQL generation and load from your given literal SQL , something along the lines of:

session.query(survey_spec).from_statement("""select survey_spec.survey_spec_id, cr.login as created_by, installed_at, req.login as requested_by, role
from survey_spec
 join (select survey_spec_id, role, max(installed_at) as installed_at from survey_installation_history group by 1, 2) latest using (survey_spec_id)
 left join survey_installation_history using (survey_spec_id, role, installed_at)
 left join users cr on created_by = cr.user_id
 left join users req on requested_by = req.user_id
where survey_id = :survey_id
order by created_at desc, installed_at desc""").params(survey_id=survey_id).all()