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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. Returns the object matching the given lookup parameters
clear() method
isnull
Entry.objects.filter(id__in=[1 - 3 - 4])
get(**kwargs)
2. 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
reverse name
annotate(args - *kwargs)
using(alias)
3. 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.
Proxy model
null
exact
order_by(*fields)
4. This model method saves a model instance to the database. This method has no return value.
save()
~
many-to-many relationship
slicing
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
intermediate models
when you add new apps to INSTALLED_APPS
Manager methods
id field
6. If this option is True - the field is allowed to be blank. Default is False.
__unicode__()
blank
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
Custom model methods
7. This sets a field to a particular value for all the objects in a QuerySet. You can only set non-relation fields and ForeignKey fields using this method.
lt
update()
filter chaining
&
8. 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
edit your settings file and change the INSTALLED_APPS setting to add the name of the module that contains your models.py.
Proxy model
Entry.objects.filter(pub_date__year=2005).delete()
primary_key
9. Defines a one-to-one relationship. You use it just like any other Field type: by including it as a class attribute of your model.
OneToOneField
week_day
select_related()
defer(*fields)
10. a QuerySet can be sliced - using Python's array-slicing syntax.
class attributes
exact
defer(*fields)
slicing
11. A Python "magic method" that returns a unicode "representation" of any object.
reverse name
Restrictions on field names
__unicode__()
model
12. A convenience method for constructing an object and saving it all in one step.
Meta class
create(**kwargs)
add()
slicing
13. 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
endswith
update(**kwargs)
class attributes
add()
14. A Manager method that returns a new QuerySet containing objects that match the given lookup parameters.
gt
filter(**kwargs)
get_absolute_url()
iteration
15. 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
Proxy model
save()
annotate(args - *kwargs)
iterator()
16. 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.
QuerySet
choices tuple
pk
many-to-one relationship
17. A manager method that returns a new QuerySet containing objects that do not match the given lookup parameters.
pickling
delete()
exclude(**kwargs)
&
18. 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.
defer(*fields)
unique
delete()
intermediate models
19. (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
Manager
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
regex
20. This model method is used for updating a ManyToManyField.
iterator()
add()
iendswith
get_or_create(**kwargs)
21. These are specified as keyword arguments to the QuerySet methods filter() - exclude() and get(). These take the form field__lookuptype=value .
Field lookups
primary_key
isnull
class type
22. If True - this field is the primary key for the model.
primary_key
only(*fields)
values_list(*fields)
distinct()
23. Operator for comparing two model instances for equality. Behind the scenes - it compares the primary key values of two models.
relationship spanning
choices
startswith
==
24. Disjunction operator for Q objects.
|
create(**kwargs)
day
Meta class
25. This query uses an F object to increment the pingback count for every entry in the blog.
Warning
: Invalid argument supplied for foreach() in
/var/www/html/basicversity.com/show_quiz.php
on line
183
26. 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.
Multi-table inheritance
blank
Manager methods
reverse()
27. 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.
get(**kwargs)
class attributes
aggregate(args - *kwargs)
Proxy model
28. When to run syncdb
primary_key
all()
when you add new apps to INSTALLED_APPS
Field lookups
29. 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)
MultipleObjectsReturned
contains
filter
30. 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.
aggregate(args - *kwargs)
filter(**kwargs)
many-to-one relationship
order_by(*fields)
31. If you pickle a QuerySet - this will force all the results to be loaded into memory prior to pickling. When you unpickle a QuerySet - it contains the results at the moment it was pickled - rather than the results that are currently in the database.
regex
endswith
Entry.objects.filter(pub_date__year=2007).update(headline='Everything is the same')
pickling
32. 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.
all()
endswith
using(alias)
create(**kwargs)
33. This is a criterion that narrow down a QuerySet based on given parameters.
Custom model methods
class attributes
year
filter
34. This query finds all entries with an id in the list [1 - 3 - 4]
relationship spanning
Entry.objects.filter(id__in=[1 - 3 - 4])
month
year
35. Lookup type for date/datetime fields that finds an exact year match. Takes a four-digit year.
Manager
year
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
all()
36. This query finds all entries with an id greater than 4.
Manager methods
extra(select=None - where=None - params=None - tables=None - order_by=None - select_params=None)
Entry.objects.filter(id__gt=4)
exists()
37. 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
update()
related_name
Field lookups
defer(*fields)
38. Lookup type that takes either True or False and corresponds to SQL queries of IS NULL and IS NOT NULL - respectively.
isnull
latest(field_name=None)
Proxy model
values(*fields)
39. Used to get a QuerySet for a model. This is called 'objects' by default.
relationship spanning
defer(*fields)
reverse name
Manager
40. If True - the table does not permit duplicate values for this field.
id field
istartswith
month
unique
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.
iregex
filter chaining
count()
delete()
42. Lookup type for date/datetime fields that finds an exact month match. Takes an integer 1 (January) through 12
OneToOneField
blank
pickling
month
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
order_by(*fields)
pickling
none()
filter(**kwargs)
44. 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.
in_bulk(id_list)
all()
get_absolute_url()
Field lookups
45. 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.
model
choices tuple
Entry.objects.filter(pub_date__range=(start_date - end_date))
Many-to-many relationship to self
46. Lookup type for date/datetime fields that finds a 'day of the week' match.
dates(field - kind - order='ASC')
week_day
ForeignKey
iregex
47. 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.
day
Entry.objects.filter(id__in=[1 - 3 - 4])
get(**kwargs)
all()
48. Lookup type that returns results less than or equal to a given value.
day
MultipleObjectsReturned
dates(field - kind - order='ASC')
lte
49. This query finds all entries between a start date of start_date and an end date of end_date.
Entry.objects.filter(pub_date__range=(start_date - end_date))
get_or_create(**kwargs)
day
Many-to-many relationship through an intermediate model
50. A convenience method for looking up an object with the given kwargs - creating one if necessary.
aggregate(args - *kwargs)
Meta class
many-to-one relationship
get_or_create(**kwargs)
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