Database Functions¶

Cast¶

class Cast(expression, output_field)[소스]¶

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

Usage example:

>>> from django.db.models import FloatField
>>> from django.db.models.functions import Cast
>>> Value.objects.create(integer=4)
>>> value = Value.objects.annotate(as_float=Cast('integer', FloatField())).get()
>>> print(value.as_float)
4.0

Coalesce¶

class Coalesce(*expressions, **extra)[소스]¶

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.

Usage examples:

>>> # 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

>>> from django.db.models import DateTimeField
>>> from django.db.models.functions import Cast, Coalesce
>>> from django.utils import timezone
>>> now = timezone.now()
>>> Coalesce('updated', Cast(now, DateTimeField()))

Greatest¶

class Greatest(*expressions, **extra)[소스]¶

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.

Usage example:

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 will be the most recent of blog.modified and comment.modified.

Least¶

class Least(*expressions, **extra)[소스]¶

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.

Extract¶

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

Extracts a component of a date as a number.

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.

Given the datetime 2015-06-15 23:30:01.000321+00:00, the built-in lookup_names return:

• "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

>>> from datetime import datetime
>>> dt = datetime(2015, 6, 15)
>>> (dt.isoweekday() % 7) + 1
2

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').

Usage example:

>>> 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

>>> from datetime import datetime
>>> from django.utils import timezone
>>> from django.db.models.functions import (
...     ExtractDay, ExtractMonth, ExtractQuarter, 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_date'),
...     quarter=ExtractQuarter('start_date'),
...     month=ExtractMonth('start_date'),
...     week=ExtractWeek('start_date'),
...     day=ExtractDay('start_date'),
...     weekday=ExtractWeekDay('start_date'),
... ).values('year', 'quarter', 'month', 'week', 'day', 'weekday').get(
...     end_date__year=ExtractYear('start_date'),
... )
{'year': 2015, 'quarter': 2, 'month': 6, 'week': 25, 'day': 15, 'weekday': 2}

>>> 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'),
...     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', 'month', 'week', 'day', 'weekday', 'hour', 'minute', 'second',
... ).get(end_datetime__year=ExtractYear('start_datetime'))
{'year': 2015, 'quarter': 2, 'month': 6, 'week': 25, 'day': 15, 'weekday': 2,
 'hour': 23, 'minute': 30, 'second': 1}

>>> 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}

>>> 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[소스]¶

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

Usage example:

>>> 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)[소스]¶

Truncates a date up to a significant component.

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.

Given the datetime 2015-06-15 14:30:50.000321+00:00, the built-in kinds return:

• "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.

Usage example:

>>> 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

>>> 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

>>> 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>)
}

>>> 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

Chr¶

class Chr(expression, **extra)[소스]¶

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.

Usage example:

>>> 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)[소스]¶

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.

Usage example:

>>> # 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)[소스]¶

Returns the first length characters of the given text field or expression.

Usage example:

>>> 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)[소스]¶

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.

Usage example:

>>> # 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)

It can also be registered as a transform. For example:

>>> 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)[소스]¶

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

It can also be registered as a transform as described in Length.

Usage example:

>>> 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

LPad¶

class LPad(expression, length, fill_text=Value(' '), **extra)[소스]¶

Returns the value of the given text field or expression padded on the left side with fill_text so that the resulting value is length characters long. The default fill_text is a space.

Usage example:

>>> from django.db.models import Value
>>> from django.db.models.functions import LPad
>>> Author.objects.create(name='John', alias='j')
>>> Author.objects.update(name=LPad('name', 8, Value('abc')))
1
>>> print(Author.objects.get(alias='j').name)
abcaJohn

LTrim¶

class LTrim(expression, **extra)[소스]¶

Similar to Trim, but removes only leading spaces.

Ord¶

class Ord(expression, **extra)[소스]¶

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.

Usage example:

>>> 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)[소스]¶

Returns the value of the given text field or expression repeated number times.

Usage example:

>>> 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)[소스]¶

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.

Usage example:

>>> 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'}]>

Right¶

class Right(expression, length, **extra)[소스]¶

Returns the last length characters of the given text field or expression.

Usage example:

>>> 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

RPad¶

class RPad(expression, length, fill_text=Value(' '), **extra)[소스]¶

Similar to LPad, but pads on the right side.

RTrim¶

class RTrim(expression, **extra)[소스]¶

Similar to Trim, but removes only trailing spaces.

StrIndex¶

class StrIndex(string, substring, **extra)[소스]¶

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.

Usage example:

>>> 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)[소스]¶

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.

Usage example:

>>> # 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)[소스]¶

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

Usage example:

>>> 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)[소스]¶

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

It can also be registered as a transform as described in Length.

Usage example:

>>> 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

CumeDist¶

class CumeDist(*expressions, **extra)[소스]¶

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)[소스]¶

Equivalent to Rank but does not have gaps.

FirstValue¶

class FirstValue(expression, **extra)[소스]¶

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)[소스]¶

Calculates the value offset by offset, and if no row exists there, returns 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)[소스]¶

Comparable to FirstValue, it calculates the last value in a given frame clause.

Lead¶

class Lead(expression, offset=1, default=None, **extra)[소스]¶

Calculates the leading value in a given frame. Both offset and default are evaluated with respect to the current row.

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

NthValue¶

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

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)[소스]¶

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)[소스]¶

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

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

The following table explains the calculation for the percentile rank of a row:

Rank¶

class Rank(*expressions, **extra)[소스]¶

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)[소스]¶

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.