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Django Queryset

Subject : it-skills

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Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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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. Returns an integer representing the number of objects in the database matching the QuerySet. This never raises exceptions.
exists()
regex
isnull
count()

2. Lookup type for date/datetime fields that finds a 'day of the week' match.
reverse name
week_day
iendswith
reverse()

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

Warning: Invalid argument supplied for foreach() in /var/www/html/basicversity.com/show_quiz.php on line 183

4. Lookup type that finds a case-insensitive regular expression match.
values_list(*fields)
many-to-many relationship
db
iregex

5. These methods are intended to do "table-wide" things.
Manager methods
Entry.objects.filter(pub_date__year=2005).delete()
get_absolute_url()
Model metadata

6. By default - results returned by a QuerySet are ordered by the ordering tuple given by the ordering option in the model's Meta. You can override this on a per-QuerySet basis by using the this method.
order_by(*fields)
exists()
delete()
Model metadata

7. Can be used to remove all many-to-many relationships for an instance
clear() method
values_list(*fields)
get(**kwargs)
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)

8. The value given in the absence of a specified value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.
db
default
order_by(*fields)
Manager

9. Fields are specified by these
default
Entry.objects.filter(pub_date__year=2005).delete()
class attributes
Q()

10. This object encapsulates a collection of keyword arguments - with the keys being field lookup types. These objects can be combined using the & and | operators - as well as negated with the ~ operator.
Q()
count()
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
class type

11. Conjuntion operator for Q objects.
Custom model methods
Field lookups
create(**kwargs)
&

12. 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.
Manager methods
lte
filter chaining
latest(field_name=None)

13. This query deletes all Entry objects with a pub_date year of 2005.
iexact
defer(*fields)
id field
Entry.objects.filter(pub_date__year=2005).delete()

14. 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.
lte
help_text
DoesNotExist
OneToOneField

15. This query finds all entries with an id in the list [1 - 3 - 4]
pk
startswith
Manager
Entry.objects.filter(id__in=[1 - 3 - 4])

16. This query updates all the headlines with pub_date in 2007 to read 'Everything is the same'.

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17. Lookup type that returns results with a case-sensitive start sequence.
startswith
in_bulk(id_list)
year
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)

18. 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.
primary_key
get(**kwargs)
iexact
reverse()

19. 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
ForeignKey
help_text
iterator()
distinct()

20. 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()
filter chaining
startswith
count()
evaluation

21. Defines a many-to-one relationship. ou use it just like any other Field type: by including it as a class attribute of your model.
one-to-one relationship
MultipleObjectsReturned
all()
ForeignKey

22. Lookup type that yields an "exact" match. If you don't provide a lookup type -- that is - if your keyword argument doesn't contain a double underscore -- the lookup type is assumed to be of this sort.
month
exact
reverse()
ordered

23. 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.
range
Field lookups
many-to-one relationship
only(*fields)

24. This method is for controlling which database the QuerySet will be evaluated against if you are using more than one database. The only argument this method takes is the alias of a database - as defined in DATABASES.
add()
model
related_name
using(alias)

25. 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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26. If you are using this attribute on a ForeignKey or ManyToManyField - you must always specify a unique reverse name for the field.
Meta class
id field
related_name
week_day

27. Disjunction operator for Q objects.
|
ManyToManyField
filter chaining
iteration

28. In some complex data-modeling situations - your models might contain a lot of fields - some of which could contain a lot of data (for example - text fields) - or require expensive processing to convert them to Python objects. If you are using the res
defer(*fields)
year
Entry.objects.filter(id__in=[1 - 3 - 4])
iteration

29. If True - the table does not permit duplicate values for this field.
lt
gte
unique
update(**kwargs)

30. Defined by a OneToOneField. You use it just like any other Field type: by including it as a class attribute of your model.
pickling
Meta class
Entry.objects.filter(pub_date__range=(start_date - end_date))
one-to-one relationship

31. Defined by a ManyToManyField. You use it just like any other Field type: by including it as a class attribute of your model.
Q()
many-to-many relationship
filter(**kwargs)
day

32. These add custom "row-level" functionality to your objects. These act on a particular model instance.
Custom model methods
endswith
Multi-table inheritance
Restrictions on field names

33. This is a criterion that narrow down a QuerySet based on given parameters.
save()
gt
exclude(**kwargs)
filter

34. 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.
lte
MultipleObjectsReturned
filter(**kwargs)
delete()

35. Each one of these is a Python class that subclasses django.db.models.Model. Each attribute of one of these represents a database field.
values_list(*fields)
OneToOneField
model
defer(*fields)

36. If True - this field is the primary key for the model.
save()
reverse name
update(**kwargs)
primary_key

37. 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.
null
save()
intermediate models
aggregate(args - *kwargs)

38. True if the QuerySet has an order_by() clause or a default ordering on the model. False otherwise.
help_text
create(**kwargs)
ordered
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)

39. Exception raised by get(**kwargs) if no items match the query.
update()
regex
class type
DoesNotExist

40. Exception raised by get(**kwargs) if more than one item matches the query.
pickling
MultipleObjectsReturned
db
none()

41. A convenience method for constructing an object and saving it all in one step.
clear() method
filter(**kwargs)
all()
create(**kwargs)

42. 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.
Many-to-many relationship through an intermediate model
choices
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
through argument

43. Returns True if the QuerySet contains any results - and False if not. This tries to perform the query in the simplest and fastest way possible - but it does execute nearly the same query. This means that calling this method on a queryset is faster th
latest(field_name=None)
exists()
Model metadata
filter chaining

44. 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.
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
Model metadata
only(*fields)
iterator()

45. 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
relationship spanning
delete()
slicing
all()

46. Lookup type for date/datetime fields that finds an exact day match.
create(**kwargs)
filter
order_by(*fields)
day

47. Lookup type that returns results greater than a given value.
create(**kwargs)
default
gt
Entry.objects.filter(pub_date__range=(start_date - end_date))

48. This model type is useful if you only want to modify the Python-level behavior of a model - without changing the models fields in any way. This creates a stand-in for the original model. You can create - delete and update instances of this new model
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
delete()
choices
Proxy model

49. This model method saves a model instance to the database. This method has no return value.
in_bulk(id_list)
save()
Many-to-many relationship through an intermediate model
in

50. 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.
day
exists()
gt
choices tuple