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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.
year
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
default
exact
2. 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)
when you add new apps to INSTALLED_APPS
Restrictions on field names
Manager
3. This query deletes all Entry objects with a pub_date year of 2005.
latest(field_name=None)
filter
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
Entry.objects.filter(pub_date__year=2005).delete()
4. This gives your model metadata.
blank
Meta class
values_list(*fields)
regex
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
regex
intermediate models
through argument
Entry.objects.filter(id__gt=4)
6. This method is more or less the opposite of defer(). You call it with the fields that should not be deferred when retrieving a model. If you have a model where almost all the fields need to be deferred - using this method to specify the complementary
only(*fields)
search
choices tuple
ForeignKey
7. Lookup type that yields a case-insensitive match.
iexact
select_related()
all()
Multi-table inheritance
8. If this option is True - Django will store empty values as NULL in the database. Default is False.
delete()
clear() method
null
reverse()
9. 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.
evaluation
get_absolute_url()
|
when you add new apps to INSTALLED_APPS
10. Lookup type that returns results with a case-insensitive start sequence.
istartswith
when you add new apps to INSTALLED_APPS
get_or_create(**kwargs)
pk
11. This model method saves a model instance to the database. This method has no return value.
dates(field - kind - order='ASC')
select_related()
save()
Many-to-many relationship through an intermediate model
12. 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.
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
choices tuple
order_by(*fields)
iterator()
13. Returns a copy of the current QuerySet (or QuerySet subclass you pass in). This can be useful in some situations where you might want to pass in either a model manager or a QuerySet and do further filtering on the result. You can safely call all() on
iregex
all()
Many-to-many relationship to self
Q(question__istartswith='What')
14. This query finds all entries with an id greater than 4.
Entry.objects.filter(id__gt=4)
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
search
update()
15. 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.
create(**kwargs)
values(*fields)
aggregate(args - *kwargs)
intermediate models
16. This query updates all the headlines with pub_date in 2007 to read 'Everything is the same'.
Warning
: Invalid argument supplied for foreach() in
/var/www/html/basicversity.com/show_quiz.php
on line
183
17. Returns a new QuerySet containing objects that match the given lookup parameters.
using(alias)
one-to-one relationship
Q()
filter(**kwargs)
18. Returns a ValuesQuerySet -- a QuerySet that returns dictionaries when used as an iterable - rather than model-instance objects.
db
values_list(*fields)
Entry.objects.filter(id__gt=4)
values(*fields)
19. 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
regex
Field lookups
through argument
exists()
20. 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)
Meta class
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
Model metadata
only(*fields)
21. This method immediately deletes the object and has no return value.
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
F()
defer(*fields)
delete()
22. 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()
Entry.objects.filter(pub_date__range=(start_date - end_date))
exact
ForeignKey
23. Returns a new QuerySet that uses SELECT DISTINCT in its SQL query. This eliminates duplicate rows from the query results.
in_bulk(id_list)
distinct()
Q(question__istartswith='What')
search
24. This model method is used for updating a ManyToManyField.
blank
add()
Entry.objects.filter(pub_date__year=2005).delete()
defer(*fields)
25. 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.
filter(**kwargs)
in_bulk(id_list)
year
Many-to-many relationship to self
26. Lookup type that returns results less than a given value.
lt
all()
Many-to-many relationship to self
Field lookups
27. Fields are specified by these
save()
blank
class attributes
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
28. Lookup type that returns results in a given list.
save()
exact
using(alias)
in
29. 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.
istartswith
values_list(*fields)
DoesNotExist
iexact
30. Lookup type that returns results greater than a given value.
gt
istartswith
|
gte
31. If True - this field is the primary key for the model.
primary_key
range
Abstract base class
only(*fields)
32. Lookup type that returns results with a case-sensitive start sequence.
startswith
month
values_list(*fields)
evaluation
33. Lookup type that returns results with a case-insensitive end sequence.
DoesNotExist
iendswith
defer(*fields)
model
34. 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.
Entry.objects.filter(pub_date__year=2005).delete()
filter(**kwargs)
using(alias)
Model metadata
35. 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
reverse()
none()
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
model
36. 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()
Entry.objects.filter(id__in=[1 - 3 - 4])
Manager methods
Entry.objects.filter(id__gt=4)
evaluation
37. Each one of these is a Python class that subclasses django.db.models.Model. Each attribute of one of these represents a database field.
search
model
only(*fields)
Q(question__istartswith='What')
38. Lookup type that returns results that fall into an inclusive date range.
aggregate(args - *kwargs)
slicing
range
update()
39. Defined by a ManyToManyField. You use it just like any other Field type: by including it as a class attribute of your model.
many-to-many relationship
values(*fields)
select_related()
get(**kwargs)
40. Lookup type that finds a case-insensitive regular expression match.
all()
iregex
filter(**kwargs)
__unicode__()
41. 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.
default
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
select_related()
filter chaining
42. Lookup type for date/datetime fields that finds an exact year match. Takes a four-digit year.
year
annotate(args - *kwargs)
reverse name
get(**kwargs)
43. 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
&
filter chaining
class type
pk
44. If you are using this attribute on a ForeignKey or ManyToManyField - you must always specify a unique reverse name for the field.
istartswith
OneToOneField
reverse()
related_name
45. Returns the object matching the given lookup parameters
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
MultipleObjectsReturned
get(**kwargs)
relationship spanning
46. (1) These cannot be Python reserved words - because that would result in a Python syntax error. (2) These cannot contain more than one underscore in a row - due to the way Django's query lookup syntax works.
Restrictions on field names
class attributes
__unicode__()
count()
47. If this option is True - the field is allowed to be blank. Default is False.
&
Meta class
blank
gt
48. 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
&
intermediate models
iexact
49. Lookup type that returns results with a case-sensitive end sequence.
get(**kwargs)
choices
all()
endswith
50. Keyword shortcut for looking up an object by primary key.
pk
get(**kwargs)
related_name
all()