Fungsi Basisdata

The classes documented below provide a way for users to use functions provided by the underlying database as annotations, aggregations, or filters in Django. Functions are also expressions, so they can be used and combined with other expressions like aggregate functions.

Kami akan menggunakan model berikut dalam contoh dari setiap fungsi:

class Author(models.Model):
    name = models.CharField(max_length=50)
    age = models.PositiveIntegerField(null=True, blank=True)
    alias = models.CharField(max_length=50, null=True, blank=True)
    goes_by = models.CharField(max_length=50, null=True, blank=True)

We don't usually recommend allowing null=True for CharField since this allows the field to have two "empty values", but it's important for the Coalesce example below.

Fungsi perbandingan dan perubahan

`Cast`

class Cast(expression, output_field)[sumber]

Forces the result type of expression to be the one from output_field.

Contoh penggunaan:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Cast
>>> Author.objects.create(age=25, name='Margaret Smith')
>>> author = Author.objects.annotate(
...    age_as_float=Cast('age', output_field=FloatField()),
... ).get()
>>> print(author.age_as_float)
25.0

`Coalesce`

class Coalesce(*expressions, **extra)[sumber]

Accepts a list of at least two field names or expressions and returns the first non-null value (note that an empty string is not considered a null value). Each argument must be of a similar type, so mixing text and numbers will result in a database error.

Contoh penggunaan:

>>> # Get a screen name from least to most public
>>> from django.db.models import Sum, Value as V
>>> from django.db.models.functions import Coalesce
>>> Author.objects.create(name='Margaret Smith', goes_by='Maggie')
>>> author = Author.objects.annotate(
...    screen_name=Coalesce('alias', 'goes_by', 'name')).get()
>>> print(author.screen_name)
Maggie

>>> # Prevent an aggregate Sum() from returning None
>>> aggregated = Author.objects.aggregate(
...    combined_age=Coalesce(Sum('age'), V(0)),
...    combined_age_default=Sum('age'))
>>> print(aggregated['combined_age'])
0
>>> print(aggregated['combined_age_default'])
None

`Greatest`

class Greatest(*expressions, **extra)[sumber]

Accepts a list of at least two field names or expressions and returns the greatest value. Each argument must be of a similar type, so mixing text and numbers will result in a database error.

Contoh penggunaan:

class Blog(models.Model):
    body = models.TextField()
    modified = models.DateTimeField(auto_now=True)

class Comment(models.Model):
    body = models.TextField()
    modified = models.DateTimeField(auto_now=True)
    blog = models.ForeignKey(Blog, on_delete=models.CASCADE)

>>> from django.db.models.functions import Greatest
>>> blog = Blog.objects.create(body='Greatest is the best.')
>>> comment = Comment.objects.create(body='No, Least is better.', blog=blog)
>>> comments = Comment.objects.annotate(last_updated=Greatest('modified', 'blog__modified'))
>>> annotated_comment = comments.get()

annotated_comment.last_updated akan menjadi paling baru dari blog.modified dan comment.modified.

`Least`

class Least(*expressions, **extra)[sumber]

Accepts a list of at least two field names or expressions and returns the least value. Each argument must be of a similar type, so mixing text and numbers will result in a database error.

`NullIf`

class NullIf(expression1, expression2)[sumber]

Accepts two expressions and returns None if they are equal, otherwise returns expression1.

Fungsi tanggal

Kami akan menggunakan model berikut dalam contoh dari setiap fungsi:

class Experiment(models.Model):
    start_datetime = models.DateTimeField()
    start_date = models.DateField(null=True, blank=True)
    start_time = models.TimeField(null=True, blank=True)
    end_datetime = models.DateTimeField(null=True, blank=True)
    end_date = models.DateField(null=True, blank=True)
    end_time = models.TimeField(null=True, blank=True)

`Extract`

class Extract(expression, lookup_name=None, tzinfo=None, **extra)[sumber]

Mengambil komponen tanggal sebagai angka.

Takes an expression representing a DateField, DateTimeField, TimeField, or DurationField and a lookup_name, and returns the part of the date referenced by lookup_name as an IntegerField. Django usually uses the databases' extract function, so you may use any lookup_name that your database supports. A tzinfo subclass, usually provided by pytz, can be passed to extract a value in a specific timezone.

Diberikan datetime 2015-06-15 23:30:01.000321+00:00, lookup_name siap-pakai mengembalikan:

"year": 2015
"iso_year": 2015
"quarter": 2
"month": 6
"day": 15
"week": 25
"week_day": 2
"hour": 23
"minute": 30
"second": 1

If a different timezone like Australia/Melbourne is active in Django, then the datetime is converted to the timezone before the value is extracted. The timezone offset for Melbourne in the example date above is +10:00. The values returned when this timezone is active will be the same as above except for:

"day": 16
"week_day": 3
"hour": 9

Each lookup_name above has a corresponding Extract subclass (listed below) that should typically be used instead of the more verbose equivalent, e.g. use ExtractYear(...) rather than Extract(..., lookup_name='year').

Contoh penggunaan:

>>> from datetime import datetime
>>> from django.db.models.functions import Extract
>>> start = datetime(2015, 6, 15)
>>> end = datetime(2015, 7, 2)
>>> Experiment.objects.create(
...    start_datetime=start, start_date=start.date(),
...    end_datetime=end, end_date=end.date())
>>> # Add the experiment start year as a field in the QuerySet.
>>> experiment = Experiment.objects.annotate(
...    start_year=Extract('start_datetime', 'year')).get()
>>> experiment.start_year
2015
>>> # How many experiments completed in the same year in which they started?
>>> Experiment.objects.filter(
...    start_datetime__year=Extract('end_datetime', 'year')).count()
1

Kutipan `DateField`

class ExtractYear(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'year'

class ExtractIsoYear(expression, tzinfo=None, **extra)[sumber]

Returns the ISO-8601 week-numbering year.

lookup_name = 'iso_year'

class ExtractMonth(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'month'

class ExtractDay(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'day'

class ExtractWeekDay(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'week_day'

class ExtractWeek(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'week'

class ExtractQuarter(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'quarter'

These are logically equivalent to Extract('date_field', lookup_name). Each class is also a Transform registered on DateField and DateTimeField as __(lookup_name), e.g. __year.

Since DateFields don't have a time component, only Extract subclasses that deal with date-parts can be used with DateField:

>>> from datetime import datetime
>>> from django.utils import timezone
>>> from django.db.models.functions import (
...     ExtractDay, ExtractMonth, ExtractQuarter, ExtractWeek,
...     ExtractWeekDay, ExtractIsoYear, ExtractYear,
... )
>>> start_2015 = datetime(2015, 6, 15, 23, 30, 1, tzinfo=timezone.utc)
>>> end_2015 = datetime(2015, 6, 16, 13, 11, 27, tzinfo=timezone.utc)
>>> Experiment.objects.create(
...    start_datetime=start_2015, start_date=start_2015.date(),
...    end_datetime=end_2015, end_date=end_2015.date())
>>> Experiment.objects.annotate(
...     year=ExtractYear('start_date'),
...     isoyear=ExtractIsoYear('start_date'),
...     quarter=ExtractQuarter('start_date'),
...     month=ExtractMonth('start_date'),
...     week=ExtractWeek('start_date'),
...     day=ExtractDay('start_date'),
...     weekday=ExtractWeekDay('start_date'),
... ).values('year', 'isoyear', 'quarter', 'month', 'week', 'day', 'weekday').get(
...     end_date__year=ExtractYear('start_date'),
... )
{'year': 2015, 'isoyear': 2015, 'quarter': 2, 'month': 6, 'week': 25,
 'day': 15, 'weekday': 2}

Kutipan `DateTimeField`

In addition to the following, all extracts for DateField listed above may also be used on DateTimeFields .

class ExtractHour(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'hour'

class ExtractMinute(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'minute'

class ExtractSecond(expression, tzinfo=None, **extra)[sumber]

lookup_name = 'second'

These are logically equivalent to Extract('datetime_field', lookup_name). Each class is also a Transform registered on DateTimeField as __(lookup_name), e.g. __minute.

Contoh-contoh DateTimeField:

>>> from datetime import datetime
>>> from django.utils import timezone
>>> from django.db.models.functions import (
...     ExtractDay, ExtractHour, ExtractMinute, ExtractMonth,
...     ExtractQuarter, ExtractSecond, ExtractWeek, ExtractWeekDay,
...     ExtractYear,
... )
>>> start_2015 = datetime(2015, 6, 15, 23, 30, 1, tzinfo=timezone.utc)
>>> end_2015 = datetime(2015, 6, 16, 13, 11, 27, tzinfo=timezone.utc)
>>> Experiment.objects.create(
...    start_datetime=start_2015, start_date=start_2015.date(),
...    end_datetime=end_2015, end_date=end_2015.date())
>>> Experiment.objects.annotate(
...     year=ExtractYear('start_datetime'),
...     isoyear=ExtractIsoYear('start_datetime'),
...     quarter=ExtractQuarter('start_datetime'),
...     month=ExtractMonth('start_datetime'),
...     week=ExtractWeek('start_datetime'),
...     day=ExtractDay('start_datetime'),
...     weekday=ExtractWeekDay('start_datetime'),
...     hour=ExtractHour('start_datetime'),
...     minute=ExtractMinute('start_datetime'),
...     second=ExtractSecond('start_datetime'),
... ).values(
...     'year', 'isoyear', 'month', 'week', 'day',
...     'weekday', 'hour', 'minute', 'second',
... ).get(end_datetime__year=ExtractYear('start_datetime'))
{'year': 2015, 'isoyear': 2015, 'quarter': 2, 'month': 6, 'week': 25,
 'day': 15, 'weekday': 2, 'hour': 23, 'minute': 30, 'second': 1}

When USE_TZ is True then datetimes are stored in the database in UTC. If a different timezone is active in Django, the datetime is converted to that timezone before the value is extracted. The example below converts to the Melbourne timezone (UTC +10:00), which changes the day, weekday, and hour values that are returned:

>>> import pytz
>>> melb = pytz.timezone('Australia/Melbourne')  # UTC+10:00
>>> with timezone.override(melb):
...    Experiment.objects.annotate(
...        day=ExtractDay('start_datetime'),
...        weekday=ExtractWeekDay('start_datetime'),
...        hour=ExtractHour('start_datetime'),
...    ).values('day', 'weekday', 'hour').get(
...        end_datetime__year=ExtractYear('start_datetime'),
...    )
{'day': 16, 'weekday': 3, 'hour': 9}

Explicitly passing the timezone to the Extract function behaves in the same way, and takes priority over an active timezone:

>>> import pytz
>>> melb = pytz.timezone('Australia/Melbourne')
>>> Experiment.objects.annotate(
...     day=ExtractDay('start_datetime', tzinfo=melb),
...     weekday=ExtractWeekDay('start_datetime', tzinfo=melb),
...     hour=ExtractHour('start_datetime', tzinfo=melb),
... ).values('day', 'weekday', 'hour').get(
...     end_datetime__year=ExtractYear('start_datetime'),
... )
{'day': 16, 'weekday': 3, 'hour': 9}

`Now`

class Now[sumber]

Returns the database server's current date and time when the query is executed, typically using the SQL CURRENT_TIMESTAMP.

Contoh penggunaan:

>>> from django.db.models.functions import Now
>>> Article.objects.filter(published__lte=Now())
<QuerySet [<Article: How to Django>]>

`Trunc`

class Trunc(expression, kind, output_field=None, tzinfo=None, **extra)[sumber]

Memotong tanggal sampai pada komponen penting.

When you only care if something happened in a particular year, hour, or day, but not the exact second, then Trunc (and its subclasses) can be useful to filter or aggregate your data. For example, you can use Trunc to calculate the number of sales per day.

Trunc takes a single expression, representing a DateField, TimeField, or DateTimeField, a kind representing a date or time part, and an output_field that's either DateTimeField(), TimeField(), or DateField(). It returns a datetime, date, or time depending on output_field, with fields up to kind set to their minimum value. If output_field is omitted, it will default to the output_field of expression. A tzinfo subclass, usually provided by pytz, can be passed to truncate a value in a specific timezone.

Diberikan datetime 2015-06-15 14:30:50.000321+00:00, kembalian kind siap-pakai:

"year": 2015-01-01 00:00:00+00:00
"quarter": 2015-04-01 00:00:00+00:00
"month": 2015-06-01 00:00:00+00:00
"week": 2015-06-15 00:00:00+00:00
"day": 2015-06-15 00:00:00+00:00
"hour": 2015-06-15 14:00:00+00:00
"minute": 2015-06-15 14:30:00+00:00
"second": 2015-06-15 14:30:50+00:00

If a different timezone like Australia/Melbourne is active in Django, then the datetime is converted to the new timezone before the value is truncated. The timezone offset for Melbourne in the example date above is +10:00. The values returned when this timezone is active will be:

"year": 2015-01-01 00:00:00+11:00
"quarter": 2015-04-01 00:00:00+10:00
"month": 2015-06-01 00:00:00+10:00
"week": 2015-06-16 00:00:00+10:00
"day": 2015-06-16 00:00:00+10:00
"hour": 2015-06-16 00:00:00+10:00
"minute": 2015-06-16 00:30:00+10:00
"second": 2015-06-16 00:30:50+10:00

The year has an offset of +11:00 because the result transitioned into daylight saving time.

Each kind above has a corresponding Trunc subclass (listed below) that should typically be used instead of the more verbose equivalent, e.g. use TruncYear(...) rather than Trunc(..., kind='year').

The subclasses are all defined as transforms, but they aren't registered with any fields, because the obvious lookup names are already reserved by the Extract subclasses.

Contoh penggunaan:

>>> from datetime import datetime
>>> from django.db.models import Count, DateTimeField
>>> from django.db.models.functions import Trunc
>>> Experiment.objects.create(start_datetime=datetime(2015, 6, 15, 14, 30, 50, 321))
>>> Experiment.objects.create(start_datetime=datetime(2015, 6, 15, 14, 40, 2, 123))
>>> Experiment.objects.create(start_datetime=datetime(2015, 12, 25, 10, 5, 27, 999))
>>> experiments_per_day = Experiment.objects.annotate(
...    start_day=Trunc('start_datetime', 'day', output_field=DateTimeField())
... ).values('start_day').annotate(experiments=Count('id'))
>>> for exp in experiments_per_day:
...     print(exp['start_day'], exp['experiments'])
...
2015-06-15 00:00:00 2
2015-12-25 00:00:00 1
>>> experiments = Experiment.objects.annotate(
...    start_day=Trunc('start_datetime', 'day', output_field=DateTimeField())
... ).filter(start_day=datetime(2015, 6, 15))
>>> for exp in experiments:
...     print(exp.start_datetime)
...
2015-06-15 14:30:50.000321
2015-06-15 14:40:02.000123

Pemotongan `DateField`

class TruncYear(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'year'

class TruncMonth(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'month'

class TruncWeek(expression, output_field=None, tzinfo=None, **extra)[sumber]

Memotong ke tengah malam pada Senin dari minggu.

kind = 'week'

class TruncQuarter(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'quarter'

These are logically equivalent to Trunc('date_field', kind). They truncate all parts of the date up to kind which allows grouping or filtering dates with less precision. expression can have an output_field of either DateField or DateTimeField.

Since DateFields don't have a time component, only Trunc subclasses that deal with date-parts can be used with DateField:

>>> from datetime import datetime
>>> from django.db.models import Count
>>> from django.db.models.functions import TruncMonth, TruncYear
>>> from django.utils import timezone
>>> start1 = datetime(2014, 6, 15, 14, 30, 50, 321, tzinfo=timezone.utc)
>>> start2 = datetime(2015, 6, 15, 14, 40, 2, 123, tzinfo=timezone.utc)
>>> start3 = datetime(2015, 12, 31, 17, 5, 27, 999, tzinfo=timezone.utc)
>>> Experiment.objects.create(start_datetime=start1, start_date=start1.date())
>>> Experiment.objects.create(start_datetime=start2, start_date=start2.date())
>>> Experiment.objects.create(start_datetime=start3, start_date=start3.date())
>>> experiments_per_year = Experiment.objects.annotate(
...    year=TruncYear('start_date')).values('year').annotate(
...    experiments=Count('id'))
>>> for exp in experiments_per_year:
...     print(exp['year'], exp['experiments'])
...
2014-01-01 1
2015-01-01 2

>>> import pytz
>>> melb = pytz.timezone('Australia/Melbourne')
>>> experiments_per_month = Experiment.objects.annotate(
...    month=TruncMonth('start_datetime', tzinfo=melb)).values('month').annotate(
...    experiments=Count('id'))
>>> for exp in experiments_per_month:
...     print(exp['month'], exp['experiments'])
...
2015-06-01 00:00:00+10:00 1
2016-01-01 00:00:00+11:00 1
2014-06-01 00:00:00+10:00 1

Pemotongan `DateTimeField`

class TruncDate(expression, **extra)[sumber]

lookup_name = 'date'

output_field = DateField()

TruncDate casts expression to a date rather than using the built-in SQL truncate function. It's also registered as a transform on DateTimeField as __date.

class TruncTime(expression, **extra)[sumber]

lookup_name = 'time'

output_field = TimeField()

TruncTime casts expression to a time rather than using the built-in SQL truncate function. It's also registered as a transform on DateTimeField as __time.

class TruncDay(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'day'

class TruncHour(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'hour'

class TruncMinute(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'minute'

class TruncSecond(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'second'

These are logically equivalent to Trunc('datetime_field', kind). They truncate all parts of the date up to kind and allow grouping or filtering datetimes with less precision. expression must have an output_field of DateTimeField.

Contoh penggunaan:

>>> from datetime import date, datetime
>>> from django.db.models import Count
>>> from django.db.models.functions import (
...     TruncDate, TruncDay, TruncHour, TruncMinute, TruncSecond,
... )
>>> from django.utils import timezone
>>> import pytz
>>> start1 = datetime(2014, 6, 15, 14, 30, 50, 321, tzinfo=timezone.utc)
>>> Experiment.objects.create(start_datetime=start1, start_date=start1.date())
>>> melb = pytz.timezone('Australia/Melbourne')
>>> Experiment.objects.annotate(
...     date=TruncDate('start_datetime'),
...     day=TruncDay('start_datetime', tzinfo=melb),
...     hour=TruncHour('start_datetime', tzinfo=melb),
...     minute=TruncMinute('start_datetime'),
...     second=TruncSecond('start_datetime'),
... ).values('date', 'day', 'hour', 'minute', 'second').get()
{'date': datetime.date(2014, 6, 15),
 'day': datetime.datetime(2014, 6, 16, 0, 0, tzinfo=<DstTzInfo 'Australia/Melbourne' AEST+10:00:00 STD>),
 'hour': datetime.datetime(2014, 6, 16, 0, 0, tzinfo=<DstTzInfo 'Australia/Melbourne' AEST+10:00:00 STD>),
 'minute': 'minute': datetime.datetime(2014, 6, 15, 14, 30, tzinfo=<UTC>),
 'second': datetime.datetime(2014, 6, 15, 14, 30, 50, tzinfo=<UTC>)
}

Pemotongan `TimeField`

class TruncHour(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'hour'

class TruncMinute(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'minute'

class TruncSecond(expression, output_field=None, tzinfo=None, **extra)[sumber]

kind = 'second'

These are logically equivalent to Trunc('time_field', kind). They truncate all parts of the time up to kind which allows grouping or filtering times with less precision. expression can have an output_field of either TimeField or DateTimeField.

Since TimeFields don't have a date component, only Trunc subclasses that deal with time-parts can be used with TimeField:

>>> from datetime import datetime
>>> from django.db.models import Count, TimeField
>>> from django.db.models.functions import TruncHour
>>> from django.utils import timezone
>>> start1 = datetime(2014, 6, 15, 14, 30, 50, 321, tzinfo=timezone.utc)
>>> start2 = datetime(2014, 6, 15, 14, 40, 2, 123, tzinfo=timezone.utc)
>>> start3 = datetime(2015, 12, 31, 17, 5, 27, 999, tzinfo=timezone.utc)
>>> Experiment.objects.create(start_datetime=start1, start_time=start1.time())
>>> Experiment.objects.create(start_datetime=start2, start_time=start2.time())
>>> Experiment.objects.create(start_datetime=start3, start_time=start3.time())
>>> experiments_per_hour = Experiment.objects.annotate(
...    hour=TruncHour('start_datetime', output_field=TimeField()),
... ).values('hour').annotate(experiments=Count('id'))
>>> for exp in experiments_per_hour:
...     print(exp['hour'], exp['experiments'])
...
14:00:00 2
17:00:00 1

>>> import pytz
>>> melb = pytz.timezone('Australia/Melbourne')
>>> experiments_per_hour = Experiment.objects.annotate(
...    hour=TruncHour('start_datetime', tzinfo=melb),
... ).values('hour').annotate(experiments=Count('id'))
>>> for exp in experiments_per_hour:
...     print(exp['hour'], exp['experiments'])
...
2014-06-16 00:00:00+10:00 2
2016-01-01 04:00:00+11:00 1

Fungsi-fungsi Matematika

Kami akan menggunakan model berikut dalam contoh-contoh fungsi matematika:

class Vector(models.Model):
    x = models.FloatField()
    y = models.FloatField()

`Abs`

class Abs(expression, **extra)[sumber]

Returns the absolute value of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Abs
>>> Vector.objects.create(x=-0.5, y=1.1)
>>> vector = Vector.objects.annotate(x_abs=Abs('x'), y_abs=Abs('y')).get()
>>> vector.x_abs, vector.y_abs
(0.5, 1.1)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Abs
>>> FloatField.register_lookup(Abs)
>>> # Get vectors inside the unit cube
>>> vectors = Vector.objects.filter(x__abs__lt=1, y__abs__lt=1)

`ACos`

class ACos(expression, **extra)[sumber]

Returns the arccosine of a numeric field or expression. The expression value must be within the range -1 to 1.

Contoh penggunaan:

>>> from django.db.models.functions import ACos
>>> Vector.objects.create(x=0.5, y=-0.9)
>>> vector = Vector.objects.annotate(x_acos=ACos('x'), y_acos=ACos('y')).get()
>>> vector.x_acos, vector.y_acos
(1.0471975511965979, 2.6905658417935308)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import ACos
>>> FloatField.register_lookup(ACos)
>>> # Get vectors whose arccosine is less than 1
>>> vectors = Vector.objects.filter(x__acos__lt=1, y__acos__lt=1)

`ASin`

class ASin(expression, **extra)[sumber]

Returns the arcsine of a numeric field or expression. The expression value must be in the range -1 to 1.

Contoh penggunaan:

>>> from django.db.models.functions import ASin
>>> Vector.objects.create(x=0, y=1)
>>> vector = Vector.objects.annotate(x_asin=ASin('x'), y_asin=ASin('y')).get()
>>> vector.x_asin, vector.y_asin
(0.0, 1.5707963267948966)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import ASin
>>> FloatField.register_lookup(ASin)
>>> # Get vectors whose arcsine is less than 1
>>> vectors = Vector.objects.filter(x__asin__lt=1, y__asin__lt=1)

`ATan`

class ATan(expression, **extra)[sumber]

Returns the arctangent of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import ATan
>>> Vector.objects.create(x=3.12, y=6.987)
>>> vector = Vector.objects.annotate(x_atan=ATan('x'), y_atan=ATan('y')).get()
>>> vector.x_atan, vector.y_atan
(1.2606282660069106, 1.428638798133829)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import ATan
>>> FloatField.register_lookup(ATan)
>>> # Get vectors whose arctangent is less than 2
>>> vectors = Vector.objects.filter(x__atan__lt=2, y__atan__lt=2)

`ATan2`

class ATan2(expression1, expression2, **extra)[sumber]

Returns the arctangent of expression1 / expression2.

Contoh penggunaan:

>>> from django.db.models.functions import ATan2
>>> Vector.objects.create(x=2.5, y=1.9)
>>> vector = Vector.objects.annotate(atan2=ATan2('x', 'y')).get()
>>> vector.atan2
0.9209258773829491

`Ceil`

class Ceil(expression, **extra)[sumber]

Returns the smallest integer greater than or equal to a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Ceil
>>> Vector.objects.create(x=3.12, y=7.0)
>>> vector = Vector.objects.annotate(x_ceil=Ceil('x'), y_ceil=Ceil('y')).get()
>>> vector.x_ceil, vector.y_ceil
(4.0, 7.0)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Ceil
>>> FloatField.register_lookup(Ceil)
>>> # Get vectors whose ceil is less than 10
>>> vectors = Vector.objects.filter(x__ceil__lt=10, y__ceil__lt=10)

`Cos`

class Cos(expression, **extra)[sumber]

Returns the cosine of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Cos
>>> Vector.objects.create(x=-8.0, y=3.1415926)
>>> vector = Vector.objects.annotate(x_cos=Cos('x'), y_cos=Cos('y')).get()
>>> vector.x_cos, vector.y_cos
(-0.14550003380861354, -0.9999999999999986)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Cos
>>> FloatField.register_lookup(Cos)
>>> # Get vectors whose cosine is less than 0.5
>>> vectors = Vector.objects.filter(x__cos__lt=0.5, y__cos__lt=0.5)

`Cot`

class Cot(expression, **extra)[sumber]

Returns the cotangent of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Cot
>>> Vector.objects.create(x=12.0, y=1.0)
>>> vector = Vector.objects.annotate(x_cot=Cot('x'), y_cot=Cot('y')).get()
>>> vector.x_cot, vector.y_cot
(-1.5726734063976826, 0.642092615934331)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Cot
>>> FloatField.register_lookup(Cot)
>>> # Get vectors whose cotangent is less than 1
>>> vectors = Vector.objects.filter(x__cot__lt=1, y__cot__lt=1)

`Degrees`

class Degrees(expression, **extra)[sumber]

Converts a numeric field or expression from radians to degrees.

Contoh penggunaan:

>>> from django.db.models.functions import Degrees
>>> Vector.objects.create(x=-1.57, y=3.14)
>>> vector = Vector.objects.annotate(x_d=Degrees('x'), y_d=Degrees('y')).get()
>>> vector.x_d, vector.y_d
(-89.95437383553924, 179.9087476710785)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Degrees
>>> FloatField.register_lookup(Degrees)
>>> # Get vectors whose degrees are less than 360
>>> vectors = Vector.objects.filter(x__degrees__lt=360, y__degrees__lt=360)

`Exp`

class Exp(expression, **extra)[sumber]

Returns the value of e (the natural logarithm base) raised to the power of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Exp
>>> Vector.objects.create(x=5.4, y=-2.0)
>>> vector = Vector.objects.annotate(x_exp=Exp('x'), y_exp=Exp('y')).get()
>>> vector.x_exp, vector.y_exp
(221.40641620418717, 0.1353352832366127)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Exp
>>> FloatField.register_lookup(Exp)
>>> # Get vectors whose exp() is greater than 10
>>> vectors = Vector.objects.filter(x__exp__gt=10, y__exp__gt=10)

`Floor`

class Floor(expression, **extra)[sumber]

Returns the largest integer value not greater than a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Floor
>>> Vector.objects.create(x=5.4, y=-2.3)
>>> vector = Vector.objects.annotate(x_floor=Floor('x'), y_floor=Floor('y')).get()
>>> vector.x_floor, vector.y_floor
(5.0, -3.0)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Floor
>>> FloatField.register_lookup(Floor)
>>> # Get vectors whose floor() is greater than 10
>>> vectors = Vector.objects.filter(x__floor__gt=10, y__floor__gt=10)

`Ln`

class Ln(expression, **extra)[sumber]

Returns the natural logarithm a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Ln
>>> Vector.objects.create(x=5.4, y=233.0)
>>> vector = Vector.objects.annotate(x_ln=Ln('x'), y_ln=Ln('y')).get()
>>> vector.x_ln, vector.y_ln
(1.6863989535702288, 5.4510384535657)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Ln
>>> FloatField.register_lookup(Ln)
>>> # Get vectors whose value greater than e
>>> vectors = Vector.objects.filter(x__ln__gt=1, y__ln__gt=1)

`Log`

class Log(expression1, expression2, **extra)[sumber]

Accepts two numeric fields or expressions and returns the logarithm of the first to base of the second.

Contoh penggunaan:

>>> from django.db.models.functions import Log
>>> Vector.objects.create(x=2.0, y=4.0)
>>> vector = Vector.objects.annotate(log=Log('x', 'y')).get()
>>> vector.log
2.0

`Mod`

class Mod(expression1, expression2, **extra)[sumber]

Accepts two numeric fields or expressions and returns the remainder of the first divided by the second (modulo operation).

Contoh penggunaan:

>>> from django.db.models.functions import Mod
>>> Vector.objects.create(x=5.4, y=2.3)
>>> vector = Vector.objects.annotate(mod=Mod('x', 'y')).get()
>>> vector.mod
0.8

`Pi`

class Pi(**extra)[sumber]

Mengembalikan nilai dari ketetapan matematika π.

`Power`

class Power(expression1, expression2, **extra)[sumber]

Accepts two numeric fields or expressions and returns the value of the first raised to the power of the second.

Contoh penggunaan:

>>> from django.db.models.functions import Power
>>> Vector.objects.create(x=2, y=-2)
>>> vector = Vector.objects.annotate(power=Power('x', 'y')).get()
>>> vector.power
0.25

`Round`

class Round(expression, **extra)[sumber]

Rounds a numeric field or expression to the nearest integer. Whether half values are rounded up or down depends on the database.

Contoh penggunaan:

>>> from django.db.models.functions import Round
>>> Vector.objects.create(x=5.4, y=-2.3)
>>> vector = Vector.objects.annotate(x_r=Round('x'), y_r=Round('y')).get()
>>> vector.x_r, vector.y_r
(5.0, -2.0)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Round
>>> FloatField.register_lookup(Round)
>>> # Get vectors whose round() is less than 20
>>> vectors = Vector.objects.filter(x__round__lt=20, y__round__lt=20)

`Sin`

class Sin(expression, **extra)[sumber]

Returns the sine of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Sin
>>> Vector.objects.create(x=5.4, y=-2.3)
>>> vector = Vector.objects.annotate(x_sin=Sin('x'), y_sin=Sin('y')).get()
>>> vector.x_sin, vector.y_sin
(-0.7727644875559871, -0.7457052121767203)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Sin
>>> FloatField.register_lookup(Sin)
>>> # Get vectors whose sin() is less than 0
>>> vectors = Vector.objects.filter(x__sin__lt=0, y__sin__lt=0)

`Sqrt`

class Sqrt(expression, **extra)[sumber]

Returns the square root of a nonnegative numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Sqrt
>>> Vector.objects.create(x=4.0, y=12.0)
>>> vector = Vector.objects.annotate(x_sqrt=Sqrt('x'), y_sqrt=Sqrt('y')).get()
>>> vector.x_sqrt, vector.y_sqrt
(2.0, 3.46410)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Sqrt
>>> FloatField.register_lookup(Sqrt)
>>> # Get vectors whose sqrt() is less than 5
>>> vectors = Vector.objects.filter(x__sqrt__lt=5, y__sqrt__lt=5)

`Tan`

class Tan(expression, **extra)[sumber]

Returns the tangent of a numeric field or expression.

Contoh penggunaan:

>>> from django.db.models.functions import Tan
>>> Vector.objects.create(x=0, y=12)
>>> vector = Vector.objects.annotate(x_tan=Tan('x'), y_tan=Tan('y')).get()
>>> vector.x_tan, vector.y_tan
(0.0, -0.6358599286615808)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Tan
>>> FloatField.register_lookup(Tan)
>>> # Get vectors whose tangent is less than 0
>>> vectors = Vector.objects.filter(x__tan__lt=0, y__tan__lt=0)

Fungsi teks

`Chr`

class Chr(expression, **extra)[sumber]

Accepts a numeric field or expression and returns the text representation of the expression as a single character. It works the same as Python's chr() function.

Like Length, it can be registered as a transform on IntegerField. The default lookup name is chr.

Contoh penggunaan:

>>> from django.db.models.functions import Chr
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.filter(name__startswith=Chr(ord('M'))).get()
>>> print(author.name)
Margaret Smith

`Concat`

class Concat(*expressions, **extra)[sumber]

Accepts a list of at least two text fields or expressions and returns the concatenated text. Each argument must be of a text or char type. If you want to concatenate a TextField() with a CharField(), then be sure to tell Django that the output_field should be a TextField(). Specifying an output_field is also required when concatenating a Value as in the example below.

This function will never have a null result. On backends where a null argument results in the entire expression being null, Django will ensure that each null part is converted to an empty string first.

Contoh penggunaan:

>>> # Get the display name as "name (goes_by)"
>>> from django.db.models import CharField, Value as V
>>> from django.db.models.functions import Concat
>>> Author.objects.create(name='Margaret Smith', goes_by='Maggie')
>>> author = Author.objects.annotate(
...     screen_name=Concat(
...         'name', V(' ('), 'goes_by', V(')'),
...         output_field=CharField()
...     )
... ).get()
>>> print(author.screen_name)
Margaret Smith (Maggie)

`Left`

class Left(expression, length, **extra)[sumber]

Mengembalikan length karakter pertama dari bidang teks atau pernyataan yang diberikan.

Contoh penggunaan:

>>> from django.db.models.functions import Left
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(first_initial=Left('name', 1)).get()
>>> print(author.first_initial)
M

`Length`

class Length(expression, **extra)[sumber]

Accepts a single text field or expression and returns the number of characters the value has. If the expression is null, then the length will also be null.

Contoh penggunaan:

>>> # Get the length of the name and goes_by fields
>>> from django.db.models.functions import Length
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(
...    name_length=Length('name'),
...    goes_by_length=Length('goes_by')).get()
>>> print(author.name_length, author.goes_by_length)
(14, None)

Itu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:

>>> from django.db.models import CharField
>>> from django.db.models.functions import Length
>>> CharField.register_lookup(Length)
>>> # Get authors whose name is longer than 7 characters
>>> authors = Author.objects.filter(name__length__gt=7)

`Lower`

class Lower(expression, **extra)[sumber]

Menerima bidang teks tunggal atau pernyataan dan mengembalikan perwakilan huruf kecil.

Itu dapat juga didaftarkan sebagai sebuah perubahan seperti digambarkan dalam Length.

Contoh penggunaan:

>>> from django.db.models.functions import Lower
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(name_lower=Lower('name')).get()
>>> print(author.name_lower)
margaret smith

`LTrim`

class LTrim(expression, **extra)[sumber]

Mirip pada Trim, tetapi hanya memindahkan spasi awal.

`Ord`

class Ord(expression, **extra)[sumber]

Accepts a single text field or expression and returns the Unicode code point value for the first character of that expression. It works similar to Python's ord() function, but an exception isn't raised if the expression is more than one character long.

It can also be registered as a transform as described in Length. The default lookup name is ord.

Contoh penggunaan:

>>> from django.db.models.functions import Ord
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(name_code_point=Ord('name')).get()
>>> print(author.name_code_point)
77

`Repeat`

class Repeat(expression, number, **extra)[sumber]

Mengembalikan nilai dari bidang teks diberikan atau pernyataan diulang number kali.

Contoh penggunaan:

>>> from django.db.models.functions import Repeat
>>> Author.objects.create(name='John', alias='j')
>>> Author.objects.update(name=Repeat('name', 3))
1
>>> print(Author.objects.get(alias='j').name)
JohnJohnJohn

`Replace`

class Replace(expression, text, replacement=Value(''), **extra)[sumber]

Replaces all occurrences of text with replacement in expression. The default replacement text is the empty string. The arguments to the function are case-sensitive.

Contoh penggunaan:

>>> from django.db.models import Value
>>> from django.db.models.functions import Replace
>>> Author.objects.create(name='Margaret Johnson')
>>> Author.objects.create(name='Margaret Smith')
>>> Author.objects.update(name=Replace('name', Value('Margaret'), Value('Margareth')))
2
>>> Author.objects.values('name')
<QuerySet [{'name': 'Margareth Johnson'}, {'name': 'Margareth Smith'}]>

`Reverse`

class Reverse(expression, **extra)[sumber]

Accepts a single text field or expression and returns the characters of that expression in reverse order.

It can also be registered as a transform as described in Length. The default lookup name is reverse.

Contoh penggunaan:

>>> from django.db.models.functions import Reverse
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(backward=Reverse('name')).get()
>>> print(author.backward)
htimS teragraM

`Right`

class Right(expression, length, **extra)[sumber]

Mengembalikan length karakter terakhir dari bidang teks atau pernyataan yang diberikan.

Contoh penggunaan:

>>> from django.db.models.functions import Right
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(last_letter=Right('name', 1)).get()
>>> print(author.last_letter)
h

`RTrim`

class RTrim(expression, **extra)[sumber]

Mirip pada Trim, namum memindahkan hanya spasi tambahan.

`StrIndex`

class StrIndex(string, substring, **extra)[sumber]

Returns a positive integer corresponding to the 1-indexed position of the first occurrence of substring inside string, or 0 if substring is not found.

Contoh penggunaan:

>>> from django.db.models import Value as V
>>> from django.db.models.functions import StrIndex
>>> Author.objects.create(name='Margaret Smith')
>>> Author.objects.create(name='Smith, Margaret')
>>> Author.objects.create(name='Margaret Jackson')
>>> Author.objects.filter(name='Margaret Jackson').annotate(
...     smith_index=StrIndex('name', V('Smith'))
... ).get().smith_index
0
>>> authors = Author.objects.annotate(
...    smith_index=StrIndex('name', V('Smith'))
... ).filter(smith_index__gt=0)
<QuerySet [<Author: Margaret Smith>, <Author: Smith, Margaret>]>

`Substr`

class Substr(expression, pos, length=None, **extra)[sumber]

Returns a substring of length length from the field or expression starting at position pos. The position is 1-indexed, so the position must be greater than 0. If length is None, then the rest of the string will be returned.

Contoh penggunaan:

>>> # Set the alias to the first 5 characters of the name as lowercase
>>> from django.db.models.functions import Lower, Substr
>>> Author.objects.create(name='Margaret Smith')
>>> Author.objects.update(alias=Lower(Substr('name', 1, 5)))
1
>>> print(Author.objects.get(name='Margaret Smith').alias)
marga

`Trim`

class Trim(expression, **extra)[sumber]

Returns the value of the given text field or expression with leading and trailing spaces removed.

Contoh penggunaan:

>>> from django.db.models.functions import Trim
>>> Author.objects.create(name='  John  ', alias='j')
>>> Author.objects.update(name=Trim('name'))
1
>>> print(Author.objects.get(alias='j').name)
John

`Upper`

class Upper(expression, **extra)[sumber]

Accepts a single text field or expression and returns the uppercase representation.

Itu dapat juga didaftarkan sebagai sebuah perubahan seperti digambarkan dalam Length.

Contoh penggunaan:

>>> from django.db.models.functions import Upper
>>> Author.objects.create(name='Margaret Smith')
>>> author = Author.objects.annotate(name_upper=Upper('name')).get()
>>> print(author.name_upper)
MARGARET SMITH

Fungsi Windows

There are a number of functions to use in a Window expression for computing the rank of elements or the Ntile of some rows.

`CumeDist`

class CumeDist(*expressions, **extra)[sumber]

Calculates the cumulative distribution of a value within a window or partition. The cumulative distribution is defined as the number of rows preceding or peered with the current row divided by the total number of rows in the frame.

`DenseRank`

class DenseRank(*expressions, **extra)[sumber]

Equivalent to Rank but does not have gaps.

`FirstValue`

class FirstValue(expression, **extra)[sumber]

Returns the value evaluated at the row that's the first row of the window frame, or None if no such value exists.

`Lag`

class Lag(expression, offset=1, default=None, **extra)[sumber]

Menghitung nilai offset oleh offset, dan jika tidak ada baris yang ada disana, mengembalikan default.

default must have the same type as the expression, however, this is only validated by the database and not in Python.

`LastValue`

class LastValue(expression, **extra)[sumber]

Dibandingkan pada FirstValue, itu menghitung nilai terakhir dalam klausa kerangka yang diberikan.

`NthValue`

class NthValue(expression, nth=1, **extra)[sumber]

Computes the row relative to the offset nth (must be a positive value) within the window. Returns None if no row exists.

Some databases may handle a nonexistent nth-value differently. For example, Oracle returns an empty string rather than None for character-based expressions. Django doesn't do any conversions in these cases.

`Ntile`

class Ntile(num_buckets=1, **extra)[sumber]

Calculates a partition for each of the rows in the frame clause, distributing numbers as evenly as possible between 1 and num_buckets. If the rows don't divide evenly into a number of buckets, one or more buckets will be represented more frequently.

`PercentRank`

class PercentRank(*expressions, **extra)[sumber]

Computes the percentile rank of the rows in the frame clause. This computation is equivalent to evaluating:

(rank - 1) / (total rows - 1)

Tabel berikut menjelaskan perhitungan untuk peringkat perseratus dari sebuah baris:

Baris #	Nilai	Peringkat	Perhitungan	Peringkat Persen
1	15	1	(1-1)/(7-1)	0.0000
2	20	2	(2-1)/(7-1)	0.1666
3	20	2	(2-1)/(7-1)	0.1666
4	20	2	(2-1)/(7-1)	0.1666
5	30	5	(5-1)/(7-1)	0.6666
6	30	5	(5-1)/(7-1)	0.6666
7	40	7	(7-1)/(7-1)	1.0000

`Rank`

class Rank(*expressions, **extra)[sumber]

Comparable to RowNumber, this function ranks rows in the window. The computed rank contains gaps. Use DenseRank to compute rank without gaps.

`RowNumber`

class RowNumber(*expressions, **extra)[sumber]

Computes the row number according to the ordering of either the frame clause or the ordering of the whole query if there is no partitioning of the window frame.

Fungsi Basisdata

Fungsi perbandingan dan perubahan

Cast

Coalesce

Greatest

Least

NullIf

Fungsi tanggal

Extract

Kutipan DateField

Kutipan DateTimeField

Now

Trunc

Pemotongan DateField

Pemotongan DateTimeField

Pemotongan TimeField

Fungsi-fungsi Matematika

Abs

ACos

ASin

ATan

ATan2

Ceil

Cos

Cot

Degrees

Exp

Floor

Ln

Log

Mod

Pi

Power

Round

Sin

Sqrt

Tan

Fungsi teks

Chr

Concat

Left

Length

Lower

LTrim

Ord

Repeat

Replace

Reverse

Right

RTrim

StrIndex

Substr

Trim

Upper

Fungsi Windows

CumeDist

DenseRank

FirstValue

Lag

LastValue

NthValue

Ntile

PercentRank

Rank

RowNumber

Additional Information

Support Django!

Contents

Getting help

Download:

`Cast`

`Coalesce`

`Greatest`

`Least`

`NullIf`

`Extract`

Kutipan `DateField`

Kutipan `DateTimeField`

`Now`

`Trunc`

Pemotongan `DateField`

Pemotongan `DateTimeField`

Pemotongan `TimeField`

`Abs`

`ACos`

`ASin`

`ATan`

`ATan2`

`Ceil`

`Cos`

`Cot`

`Degrees`

`Exp`

`Floor`

`Ln`

`Log`

`Mod`

`Pi`

`Power`

`Round`

`Sin`

`Sqrt`

`Tan`

`Chr`

`Concat`

`Left`

`Length`

`Lower`

`LTrim`

`Ord`

`Repeat`

`Replace`

`Reverse`

`Right`

`RTrim`

`StrIndex`

`Substr`

`Trim`

`Upper`

`CumeDist`

`DenseRank`

`FirstValue`

`Lag`

`LastValue`

`NthValue`

`Ntile`

`PercentRank`

`Rank`

`RowNumber`