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Test your basic knowledge |
Django Queryset
Start Test
Study First
Subject
:
it-skills
Instructions:
Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can
study here
.
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. 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)
Entry.objects.filter(id__gt=4)
ManyToManyField
Restrictions on field names
2. 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
Proxy model
Abstract base class
iendswith
edit your settings file and change the INSTALLED_APPS setting to add the name of the module that contains your models.py.
3. 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.
Entry.objects.filter(pub_date__range=(start_date - end_date))
help_text
Q()
aggregate(args - *kwargs)
4. True if the QuerySet has an order_by() clause or a default ordering on the model. False otherwise.
many-to-many relationship
|
ManyToManyField
ordered
5. 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
|
Q(question__istartswith='What')
intermediate models
Many-to-many relationship to self
6. This method immediately deletes the object and has no return value.
delete()
class type
many-to-one relationship
add()
7. 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
all()
OneToOneField
Proxy model
==
8. 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.
help_text
order_by(*fields)
using(alias)
Field lookups
9. Returns the most recent object in the table - by date - using the field_name provided as the date field.
ordered
regex
latest(field_name=None)
F()
10. This model method saves a model instance to the database. This method has no return value.
iteration
values(*fields)
save()
ManyToManyField
11. 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
using(alias)
filter chaining
select_related()
ordered
12. Lookup type for date/datetime fields that finds an exact year match. Takes a four-digit year.
year
using(alias)
in
Abstract base class
13. Lookup type that finds a case-insensitive regular expression match.
ManyToManyField
iregex
Proxy model
intermediate models
14. These are specified as keyword arguments to the QuerySet methods filter() - exclude() and get(). These take the form field__lookuptype=value .
iendswith
Field lookups
contains
order_by(*fields)
15. This method returns tuples of values when iterated over. Each tuple contains the value from the respective field passed into the call to this method -- so the first item is the first field - etc.
only(*fields)
range
ManyToManyField
values_list(*fields)
16. Here - you can't use add - create - or assignment (i.e. - beatles.members = [...]) to create relationships. You need to specify all the detail for the relationship required by the intermediate model.
save()
Many-to-many relationship through an intermediate model
many-to-many relationship
Model metadata
17. 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
many-to-one relationship
all()
using(alias)
18. Operator for comparing two model instances for equality. Behind the scenes - it compares the primary key values of two models.
add()
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
==
model
19. If you are using this attribute on a ForeignKey or ManyToManyField - you must always specify a unique reverse name for the field.
evaluation
related_name
db
intermediate models
20. A Q object that asks for entries with a question value that start with 'Who' or do not have a publication date of 2005.
21. 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.
many-to-one relationship
when you add new apps to INSTALLED_APPS
null
get_or_create(**kwargs)
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.
count()
values(*fields)
exact
distinct()
23. 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.
lte
primary_key
annotate(args - *kwargs)
ForeignKey
24. This represents a collection of objects from your database. It can have zero - one or many filters.
==
iterator()
pk
QuerySet
25. Lookup type that corresponds to a boolean full-text search - taking advantage of full-text indexing. This is like contains but is significantly faster due to full-text indexing.
count()
clear() method
update(**kwargs)
search
26. 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
annotate(args - *kwargs)
DoesNotExist
Many-to-many relationship through an intermediate model
reverse name
27. Keyword shortcut for looking up an object by primary key.
day
Entry.objects.filter(pub_date__year=2005).delete()
dates(field - kind - order='ASC')
pk
28. Fields are specified by these
in
Proxy model
class attributes
values_list(*fields)
29. Lookup type that returns results greater than a given value.
gt
update(**kwargs)
MultipleObjectsReturned
evaluation
30. If True - the table does not permit duplicate values for this field.
unique
Entry.objects.filter(pub_date__year=2005).delete()
many-to-many relationship
order_by(*fields)
31. This query finds all entries with an id greater than 4.
day
year
get_absolute_url()
Entry.objects.filter(id__gt=4)
32. a QuerySet can be sliced - using Python's array-slicing syntax.
__unicode__()
in
evaluation
slicing
33. 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
ManyToManyField
Abstract base class
none()
Meta class
34. 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.
Multi-table inheritance
intermediate models
count()
Entry.objects.filter(pub_date__range=(start_date - end_date))
35. If this option is True - Django will store empty values as NULL in the database. Default is False.
filter chaining
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
when you add new apps to INSTALLED_APPS
null
36. Takes a list of primary-key values and returns a dictionary mapping each primary-key value to an instance of the object with the given ID.
iregex
in_bulk(id_list)
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
37. 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.
intermediate models
delete()
istartswith
class type
38. If this option is True - the field is allowed to be blank. Default is False.
blank
in_bulk(id_list)
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
Abstract base class
39. 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.
reverse()
range
ForeignKey
iexact
40. This query finds all entries with an id in the list [1 - 3 - 4]
ForeignKey
Entry.objects.filter(id__in=[1 - 3 - 4])
add()
get(**kwargs)
41. Negation operator for Q objects.
primary_key
many-to-one relationship
slicing
~
42. These are "anything that's not a field" - such as ordering options (ordering) - database table name (db_table) - or human-readable singular and plural names (verbose_name and verbose_name_plural)
exclude(**kwargs)
primary_key
Model metadata
in
43. This gives your model metadata.
Meta class
ForeignKey
count()
order_by(*fields)
44. Exception raised by get(**kwargs) if more than one item matches the query.
Many-to-many relationship to self
delete()
MultipleObjectsReturned
ManyToManyField
45. Lookup type that tests for inclusion in a case-sensitive fashion.
only(*fields)
default
contains
gt
46. 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
delete()
iterator()
DoesNotExist
null
47. Manager method used to retrieve every object in a model.
|
get_or_create(**kwargs)
all()
distinct()
48. what the field _______ determines: (1) The database column type (e.g. INTEGER - VARCHAR); (2) The widget to use in Django's admin interface - if you care to use it (e.g. <input type="text"> - <select>); (3) The minimal validation requirements - used
class type
day
aggregate(args - *kwargs)
month
49. Exception raised by get(**kwargs) if no items match the query.
Field lookups
DoesNotExist
Abstract base class
iregex
50. Lookup type that returns results with a case-insensitive end sequence.
all()
MultipleObjectsReturned
pickling
iendswith