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Django Queryset

Subject : it-skills

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. Lookup type for date/datetime fields that finds a 'day of the week' match.
get_or_create(**kwargs)
week_day
db
isnull

2. Sometimes - the Django query syntax by itself can't easily express a complex WHERE clause. For these edge cases - Django provides this QuerySet modifier -- a hook for injecting specific clauses into the SQL generated by a QuerySet.
all()
exclude(**kwargs)
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
id field

3. Returns a new QuerySet that uses SELECT DISTINCT in its SQL query. This eliminates duplicate rows from the query results.
distinct()
isnull
get(**kwargs)
Restrictions on field names

4. Defined by a OneToOneField. You use it just like any other Field type: by including it as a class attribute of your model.
reverse name
filter(**kwargs)
gt
one-to-one relationship

5. A manager method which returns a single object. If there are no results that match the query - this method will raise a DoesNotExist exception. If more than one item matches this query - the method will raise MultipleObjectsReturned.
contains
model
pk
get(**kwargs)

6. Adds to each object in the QuerySet with the provided list of aggregate values (averages - sums - etc) that have been computed over the objects that are related to the objects in the QuerySet. Each argument to this is content that will be added to ea
month
annotate(args - *kwargs)
OneToOneField
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)

7. This tells Django how to calculate the URL for an object. Django uses this in its admin interface - and any time it needs to figure out a URL for an object.
db
defer(*fields)
iexact
get_absolute_url()

8. Specifies the model that will be used to govern the many-to-many relationship. You can then put extra fields on the intermediate model. The intermediate model is associated with the ManyToManyField using this to point to the model that will act as an
ManyToManyField
clear() method
through argument
count()

9. A Q object that encapsulates queries for entries with a question value that starts with 'What' in a case-insensitive fashion.

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10. Defines a many-to-many relationship. You use it just like any other Field type: by including it as a class attribute of your model.
in
id field
only(*fields)
ManyToManyField

11. Returns the object matching the given lookup parameters
month
save()
QuerySet
get(**kwargs)

12. Evaluates the QuerySet (by performing the query) and returns an iterator over the results. A QuerySet typically caches its results internally so that repeated evaluations do not result in additional queries; this method will instead read results dire
lte
endswith
iterator()
all()

13. Defined by a ManyToManyField. You use it just like any other Field type: by including it as a class attribute of your model.
add()
year
MultipleObjectsReturned
many-to-many relationship

14. This style of inheritanc is useful when you're subclassing an existing model (perhaps something from another application entirely) and want each model to have its own database table. Here - each model in the hierarchy is a model all by itself.
db
reverse name
Multi-table inheritance
Meta class

15. Returns a QuerySet that will automatically "follow" foreign-key relationships - selecting that additional related-object data when it executes its query. This is a performance booster which results in (sometimes much) larger queries but means later u
select_related()
update()
get_or_create(**kwargs)
slicing

16. restrictions on ________: (1) Your intermediate model must contain one - and only one - foreign key to the target model. (2) Your intermediate model must contain one - and only one - foreign key to the source model. (3) When defining a many-to-many r
one-to-one relationship
intermediate models
month
ForeignKey

17. Returns a new QuerySet containing objects that match the given lookup parameters.
reverse name
slicing
values_list(*fields)
filter(**kwargs)

18. When to run syncdb
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
reverse()
when you add new apps to INSTALLED_APPS
default

19. Lookup type that returns results with a case-sensitive start sequence.
filter
DoesNotExist
startswith
related_name

20. Returns the most recent object in the table - by date - using the field_name provided as the date field.
F()
class type
get(**kwargs)
latest(field_name=None)

21. If you are using this attribute on a ForeignKey or ManyToManyField - you must always specify a unique reverse name for the field.
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
gt
Custom model methods
related_name

22. The first element in this iterable is the value that will be stored in the database - the second element will be displayed by the admin interface - or in a ModelChoiceField.
choices tuple
in_bulk(id_list)
Abstract base class
Entry.objects.filter(id__gt=4)

23. A Q object that asks for entries with a question value that start with 'Who' or do not have a publication date of 2005.

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24. A QuerySet is iterable - and it executes its database query the first time you iterate over it.
startswith
all()
Manager methods
iteration

25. Accomplish this by using the field name of related fields across models - separated by double underscores - until you get to the field you want. For example - to get all Entry objects with a Blog whose name is 'Beatles Blog': Entry.objects.filter(blo
filter(**kwargs)
|
clear() method
relationship spanning

26. The default for this is the name of the child class followed by '_set'.
class attributes
reverse name
aggregate(args - *kwargs)
count()

27. This class type is useful when you just want to use the parent class to hold information that you don't want to have to type out for each child model. This class isn't going to ever be used in isolation. When it is used as a base class for other mode
Abstract base class
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
iendswith
default

28. Takes the ouput of one filter and uses it as input for another filter. This works because a refinement of a QuerySet is itself a QuerySet.
regex
relationship spanning
filter chaining
pk

29. Returns a ValuesQuerySet -- a QuerySet that returns dictionaries when used as an iterable - rather than model-instance objects.
reverse()
values(*fields)
get(**kwargs)
distinct()

30. This method immediately deletes the object and has no return value.
Field lookups
iterator()
delete()
pk

31. Used to get a QuerySet for a model. This is called 'objects' by default.
help_text
blank
Manager
evaluation

32. Extra text to be displayed under the field on the object's admin form to provide assistance to users. It's useful for documentation even if your object doesn't have an admin form.
help_text
delete()
~
count()

33. If True - the table does not permit duplicate values for this field.
pk
unique
filter chaining
Manager

34. This represents a collection of objects from your database. It can have zero - one or many filters.
null
many-to-one relationship
QuerySet
regex

35. Lookup type that returns results with a case-insensitive start sequence.
day
istartswith
Manager methods
only(*fields)

36. Lookup type that returns results greater than or equal to a given value.
search
gte
Field lookups
year

37. Evaluation happens upon use the "step" parameter of slice syntax - the first time you iterate over it - when pickling or caching results - upon calling repr() - upon calling len() - upon calling list() - upon calling bool()
pk
filter(**kwargs)
aggregate(args - *kwargs)
evaluation

38. This object allows you to compare the value of a model field with another field on the same model. Django supports the use of addition - subtraction - multiplication - division and modulo arithmetic with these objects - both with constants and with o
Manager
F()
clear() method
Many-to-many relationship through an intermediate model

39. This query deletes all Entry objects with a pub_date year of 2005.
values_list(*fields)
istartswith
Entry.objects.filter(pub_date__year=2005).delete()
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)

40. Performs an SQL update query for the specified fields - and returns the number of rows affected. This method is applied instantly and the only restriction on the QuerySet that is updated is that it can only update columns in the model's main table. F
update(**kwargs)
all()
filter(**kwargs)
class type

41. Returns a DateQuerySet -- a QuerySet that evaluates to a list of datetime.datetime objects representing all available dates of a particular kind within the contents of the QuerySet.

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42. Use this method to reverse the order in which a queryset's elements are returned. Calling this method a second time restores the ordering back to the normal direction.
DoesNotExist
add()
reverse()
filter(**kwargs)

43. Returns an EmptyQuerySet -- a QuerySet that always evaluates to an empty list. This can be used in cases where you know that you should return an empty result set and your caller is expecting a QuerySet object (instead of returning an empty list - fo
none()
delete()
get_or_create(**kwargs)
filter chaining

44. In this case - an intermediate model can have multiple foreign keys to the source model. Here - two foreign keys to the same model are permitted - but they will be treated as the two (different) sides of the many-to-many relation.
Many-to-many relationship to self
unique
when you add new apps to INSTALLED_APPS
all()

45. This model method saves a model instance to the database. This method has no return value.
model
relationship spanning
save()
primary_key

46. A convenience method for constructing an object and saving it all in one step.
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
filter(**kwargs)
choices tuple
create(**kwargs)

47. An iterable (e.g. - a list or tuple) of 2-tuples to use as options for this field. If this is given - Django's admin will use a select box instead of the standard text field and will limit options to those given.
reverse name
in
relationship spanning
choices

48. Performs an SQL delete query on all rows in the QuerySet. This method is applied instantly. You cannot call this method on a QuerySet that has had a slice taken or can otherwise no longer be filtered.
QuerySet
filter(**kwargs)
class attributes
delete()

49. Returns a dictionary of aggregate values (averages - sums - etc) calculated over the QuerySet. Each argument to this method specifies a value that will be included in the dictionary that is returned.
filter chaining
Proxy model
aggregate(args - *kwargs)
iterator()

50. Defined by django.db.models.ForeignKey. You use it just like any other Field type: by including it as a class attribute of your model.
unique
order_by(*fields)
many-to-one relationship
gte