Wie kann ich diese Abfrage in sqlalchemy ORM ausdrücken?

Question

Hier ist meine SQL-Abfrage:

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 

Ich habe ORM Einheiten für survey_spec, survey_installation_history und users und survey_spec.installations ist eine Beziehung zu survey_installation_historysurvey_spec_id als Schlüssel.

Answer 1

Haben Sie die Beispielausgabe von dem, was Sie bisher bekommen haben? das heißt, die Ausgabe von:

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

Wenn Sie nur Ihre Entitäten wollen laden, können Sie die SQL-Generierung und die Last von Ihren umgehen literal SQL, etwas entlang der Linien von gegeben:

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()