Django将MySQL查询翻译成Django查询

Question

How can i get the equivalent of this MySQL script in Django views? The depart_city, arrive_city, and travel_date will be inputed by the user.

Here is my Models

class Driver(models.Model):
first_name = models.CharField(max_length=30, null=True, blank=False)
last_name = models.CharField(max_length=30, null=True, blank=False)




class Schedule(models.Model):
depart_time = models.TimeField()
arrive_time = models.TimeField()



class TravelDate(models.Model):
start_date = models.DateField(null = True)
interval = models.IntegerField(null = True) 


class Route(models.Model): 
depart_city = models.CharField(max_length=50, null=True, blank=False)
arrive_city = models.CharField(max_length=50, null=True, blank=False)
driver = models.ForeignKey(Driver)
schedule = models.ForeignKey(Schedule)
traveldate = models.ForeignKey(TravelDate)

Here is my MySQL script. This works when i run it on MySQL workbench but I'm not sure how to translate this to Django Query

    SELECT busapp_route.depart_city, busapp_route.arrive_city, busapp_driver.first_name, busapp_schedule.depart_time 
FROM (((busapp_route INNER JOIN busapp_driver ON busapp_route.driver_id = busapp_driver.id) 
INNER JOIN busapp_schedule ON busapp_route.schedule_id = busapp_schedule.id)
INNER JOIN busapp_traveldate ON busapp_route.traveldate_id = busapp_traveldate.id) 
WHERE busapp_route.depart_city='Tropoje' AND busapp_route.arrive_city='Tirane'
AND (DATEDIFF('2017-11-26', busapp_traveldate.start_date) % busapp_traveldate.interval = 0);

Answer 1

Django doesn't support MySQL DATEDIFF natively. As a workaround, you could use something like this:

from django.db.models.expressions import RawSQL

routes = Route.objects\
    .values('depart_city', 'arrive_city', 'driver__first_name', 'schedule__depart_time', 'traveldate__start_date')\
    .annotate(datediff_mod=RawSQL("DATEDIFF(%s, busapp_traveldate.start_date) MOD busapp_traveldate.interval", ('2017-11-26', )))\
    .filter(depart_city='Tropoje', arrive_city='Tirane', datediff_mod = 0)

I don't use MySQL so I couldn't test this, but I'm pretty sure it should work or maybe at least give you an idea how to implement it.

Answer 2

I don't think that it's a good idea, trying to solve this from the SQL side.

And what you're building there, is not trivial as there are a lot of things to keep in mind.

Your current Model setup lags some points: What if a user searches for a travel in next year? With your model you'll have to create entries for all possible dates in the future, that's nearly unusable.

Think also about separating times and dates in different models, as they usually should be kept together, cause a ride from A to B at date x and time y is one object.

It might help to have a look at django-scheduler , they solved some troubles with the use of Events and Occurences. Have a look at their pretty good docs.