On Mar 1, 6:46 pm, koranthala <koranth...@gmail.com> wrote: > Hi, > This is my first Django/DB project, so pardon for the naivete of > the question. > > I have one relation in my DB which I cannot - whatever I think of > - seem to do it in a single DB check. Since I have around 5 other > separate SQL statements in that same view, I am worried about the > performance of the system. Is it possible for someone to help me out > how to do it in a single DB check? > > Models: > class CarType(models.Model): > type models.Charfield(max_length=32) > > class CarName(models.Model); > name models.CharField(max_length=32, unique=True) > cartype models.ForeignKey(CarType) > > class Buyers(models.Model): > invoice models.IntegerField() > ... > cartype models.ForeignKey(CarType) > > Now, I have input as car name, which is associated with the car type. > I need to get the buyer details wherein the car type is the same as > the cartype associated with the car name. > Currently, I do the following; > carNameObj = CarName.objects.filter(name__exact=iName) > buyerDetails = Buyers.objects.filter > (cartype__exact=carNameObj.cartype) > > As can be seen, there are two separate DB checks for something which I > feel should be done in a single DB check. Is it possible for someone > to help me out?
There's some information missing here. In particular, the two statements above could never execute, becuase CarName.objects.filter() returns a queryset, which doesn't have a cartype attribute. It would have helped to post the actual view you're running? Secondly, I wouldn't worry too much about query counts. 5 SQL queries doesn't seem like very many to me. Databases are good at this stuff, and unless you've got extremely low-powered hardware or are expecting a huge number of users, it shouldn't be a concern. Your question should be whether it is fast enough. (As a side point, don't make the mistake of equating the number of ORM calls with the number of SQL statements - one ORM call might be one SQL query, or many... or many ORM calls might result in just one SQL query. If you're worried about actual SQL counts, your best bet is to use some sort of profiling middleware - there are various examples on djangosnippets.com). However, the query you want should be quite simple: buyerDetails = Buyers.objects.filter(cartype__carname__name=iName) -- DR. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
