The classes documented below provide a way for users to use functions provided\nby the underlying database as annotations, aggregations, or filters in Django.\nFunctions are also expressions, so they can be used and\ncombined with other expressions like aggregate functions.
\nKami akan menggunakan model berikut dalam contoh dari setiap fungsi:
\nclass Author(models.Model):\n name = models.CharField(max_length=50)\n age = models.PositiveIntegerField(null=True, blank=True)\n alias = models.CharField(max_length=50, null=True, blank=True)\n goes_by = models.CharField(max_length=50, null=True, blank=True)\nWe don't usually recommend allowing null=True for CharField since this\nallows the field to have two "empty values", but it's important for the\nCoalesce example below.
CastLink to this heading#Forces the result type of expression to be the one from output_field.
Contoh penggunaan:
\n>>> from django.db.models import FloatField\n>>> from django.db.models.functions import Cast\n>>> Value.objects.create(integer=4)\n>>> value = Value.objects.annotate(as_float=Cast('integer', FloatField())).get()\n>>> print(value.as_float)\n4.0\nCoalesceLink to this heading#Accepts a list of at least two field names or expressions and returns the\nfirst non-null value (note that an empty string is not considered a null\nvalue). Each argument must be of a similar type, so mixing text and numbers\nwill result in a database error.
\nContoh penggunaan:
\n>>> # Get a screen name from least to most public\n>>> from django.db.models import Sum, Value as V\n>>> from django.db.models.functions import Coalesce\n>>> Author.objects.create(name='Margaret Smith', goes_by='Maggie')\n>>> author = Author.objects.annotate(\n... screen_name=Coalesce('alias', 'goes_by', 'name')).get()\n>>> print(author.screen_name)\nMaggie\n\n>>> # Prevent an aggregate Sum() from returning None\n>>> aggregated = Author.objects.aggregate(\n... combined_age=Coalesce(Sum('age'), V(0)),\n... combined_age_default=Sum('age'))\n>>> print(aggregated['combined_age'])\n0\n>>> print(aggregated['combined_age_default'])\nNone\nGreatestLink to this heading#Accepts a list of at least two field names or expressions and returns the\ngreatest value. Each argument must be of a similar type, so mixing text and\nnumbers will result in a database error.
\nContoh penggunaan:
\nclass Blog(models.Model):\n body = models.TextField()\n modified = models.DateTimeField(auto_now=True)\n\nclass Comment(models.Model):\n body = models.TextField()\n modified = models.DateTimeField(auto_now=True)\n blog = models.ForeignKey(Blog, on_delete=models.CASCADE)\n\n>>> from django.db.models.functions import Greatest\n>>> blog = Blog.objects.create(body='Greatest is the best.')\n>>> comment = Comment.objects.create(body='No, Least is better.', blog=blog)\n>>> comments = Comment.objects.annotate(last_updated=Greatest('modified', 'blog__modified'))\n>>> annotated_comment = comments.get()\nannotated_comment.last_updated akan menjadi paling baru dari blog.modified dan comment.modified.
LeastLink to this heading#Accepts a list of at least two field names or expressions and returns the\nleast value. Each argument must be of a similar type, so mixing text and numbers\nwill result in a database error.
\n\nKami akan menggunakan model berikut dalam contoh dari setiap fungsi:
\nclass Experiment(models.Model):\n start_datetime = models.DateTimeField()\n start_date = models.DateField(null=True, blank=True)\n start_time = models.TimeField(null=True, blank=True)\n end_datetime = models.DateTimeField(null=True, blank=True)\n end_date = models.DateField(null=True, blank=True)\n end_time = models.TimeField(null=True, blank=True)\nExtractLink to this heading#Mengambil komponen tanggal sebagai angka.
\nTakes an expression representing a DateField, DateTimeField,\nTimeField, or DurationField and a lookup_name, and returns the part\nof the date referenced by lookup_name as an IntegerField.\nDjango usually uses the databases' extract function, so you may use any\nlookup_name that your database supports. A tzinfo subclass, usually\nprovided 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
"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\nthe datetime is converted to the timezone before the value is extracted. The\ntimezone offset for Melbourne in the example date above is +10:00. The values\nreturned 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\nbelow) that should typically be used instead of the more verbose equivalent,\ne.g. use ExtractYear(...) rather than Extract(..., lookup_name='year').
Contoh penggunaan:
\n>>> from datetime import datetime\n>>> from django.db.models.functions import Extract\n>>> start = datetime(2015, 6, 15)\n>>> end = datetime(2015, 7, 2)\n>>> Experiment.objects.create(\n... start_datetime=start, start_date=start.date(),\n... end_datetime=end, end_date=end.date())\n>>> # Add the experiment start year as a field in the QuerySet.\n>>> experiment = Experiment.objects.annotate(\n... start_year=Extract('start_datetime', 'year')).get()\n>>> experiment.start_year\n2015\n>>> # How many experiments completed in the same year in which they started?\n>>> Experiment.objects.filter(\n... start_datetime__year=Extract('end_datetime', 'year')).count()\n1\nDateFieldLink to this heading#These are logically equivalent to Extract('date_field', lookup_name). Each\nclass is also a Transform registered on DateField and DateTimeField\nas __(lookup_name), e.g. __year.
Since DateFields don't have a time component, only Extract subclasses\nthat deal with date-parts can be used with DateField:
>>> from datetime import datetime\n>>> from django.utils import timezone\n>>> from django.db.models.functions import (\n... ExtractDay, ExtractMonth, ExtractQuarter, ExtractWeek,\n... ExtractWeekDay, ExtractYear,\n... )\n>>> start_2015 = datetime(2015, 6, 15, 23, 30, 1, tzinfo=timezone.utc)\n>>> end_2015 = datetime(2015, 6, 16, 13, 11, 27, tzinfo=timezone.utc)\n>>> Experiment.objects.create(\n... start_datetime=start_2015, start_date=start_2015.date(),\n... end_datetime=end_2015, end_date=end_2015.date())\n>>> Experiment.objects.annotate(\n... year=ExtractYear('start_date'),\n... quarter=ExtractQuarter('start_date'),\n... month=ExtractMonth('start_date'),\n... week=ExtractWeek('start_date'),\n... day=ExtractDay('start_date'),\n... weekday=ExtractWeekDay('start_date'),\n... ).values('year', 'quarter', 'month', 'week', 'day', 'weekday').get(\n... end_date__year=ExtractYear('start_date'),\n... )\n{'year': 2015, 'quarter': 2, 'month': 6, 'week': 25, 'day': 15, 'weekday': 2}\nDateTimeFieldLink to this heading#In addition to the following, all extracts for DateField listed above may\nalso be used on DateTimeFields .
These are logically equivalent to Extract('datetime_field', lookup_name).\nEach class is also a Transform registered on DateTimeField as\n__(lookup_name), e.g. __minute.
Contoh-contoh DateTimeField:
>>> from datetime import datetime\n>>> from django.utils import timezone\n>>> from django.db.models.functions import (\n... ExtractDay, ExtractHour, ExtractMinute, ExtractMonth,\n... ExtractQuarter, ExtractSecond, ExtractWeek, ExtractWeekDay,\n... ExtractYear,\n... )\n>>> start_2015 = datetime(2015, 6, 15, 23, 30, 1, tzinfo=timezone.utc)\n>>> end_2015 = datetime(2015, 6, 16, 13, 11, 27, tzinfo=timezone.utc)\n>>> Experiment.objects.create(\n... start_datetime=start_2015, start_date=start_2015.date(),\n... end_datetime=end_2015, end_date=end_2015.date())\n>>> Experiment.objects.annotate(\n... year=ExtractYear('start_datetime'),\n... quarter=ExtractQuarter('start_datetime'),\n... month=ExtractMonth('start_datetime'),\n... week=ExtractWeek('start_datetime'),\n... day=ExtractDay('start_datetime'),\n... weekday=ExtractWeekDay('start_datetime'),\n... hour=ExtractHour('start_datetime'),\n... minute=ExtractMinute('start_datetime'),\n... second=ExtractSecond('start_datetime'),\n... ).values(\n... 'year', 'month', 'week', 'day', 'weekday', 'hour', 'minute', 'second',\n... ).get(end_datetime__year=ExtractYear('start_datetime'))\n{'year': 2015, 'quarter': 2, 'month': 6, 'week': 25, 'day': 15, 'weekday': 2,\n 'hour': 23, 'minute': 30, 'second': 1}\nWhen USE_TZ is True then datetimes are stored in the database\nin UTC. If a different timezone is active in Django, the datetime is converted\nto that timezone before the value is extracted. The example below converts to\nthe Melbourne timezone (UTC +10:00), which changes the day, weekday, and hour\nvalues that are returned:
>>> import pytz\n>>> melb = pytz.timezone('Australia/Melbourne') # UTC+10:00\n>>> with timezone.override(melb):\n... Experiment.objects.annotate(\n... day=ExtractDay('start_datetime'),\n... weekday=ExtractWeekDay('start_datetime'),\n... hour=ExtractHour('start_datetime'),\n... ).values('day', 'weekday', 'hour').get(\n... end_datetime__year=ExtractYear('start_datetime'),\n... )\n{'day': 16, 'weekday': 3, 'hour': 9}\nExplicitly passing the timezone to the Extract function behaves in the same\nway, and takes priority over an active timezone:
>>> import pytz\n>>> melb = pytz.timezone('Australia/Melbourne')\n>>> Experiment.objects.annotate(\n... day=ExtractDay('start_datetime', tzinfo=melb),\n... weekday=ExtractWeekDay('start_datetime', tzinfo=melb),\n... hour=ExtractHour('start_datetime', tzinfo=melb),\n... ).values('day', 'weekday', 'hour').get(\n... end_datetime__year=ExtractYear('start_datetime'),\n... )\n{'day': 16, 'weekday': 3, 'hour': 9}\nNowLink to this heading#Returns the database server's current date and time when the query is executed,\ntypically using the SQL CURRENT_TIMESTAMP.
Contoh penggunaan:
\n>>> from django.db.models.functions import Now\n>>> Article.objects.filter(published__lte=Now())\n<QuerySet [<Article: How to Django>]>\nTruncLink to this heading#Memotong tanggal sampai pada komponen penting.
\nWhen you only care if something happened in a particular year, hour, or day,\nbut not the exact second, then Trunc (and its subclasses) can be useful to\nfilter or aggregate your data. For example, you can use Trunc to calculate\nthe number of sales per day.
Trunc takes a single expression, representing a DateField,\nTimeField, or DateTimeField, a kind representing a date or time\npart, and an output_field that's either DateTimeField(),\nTimeField(), or DateField(). It returns a datetime, date, or time\ndepending on output_field, with fields up to kind set to their minimum\nvalue. If output_field is omitted, it will default to the output_field\nof expression. A tzinfo subclass, usually provided by pytz, can be\npassed 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\nthe datetime is converted to the new timezone before the value is truncated.\nThe timezone offset for Melbourne in the example date above is +10:00. The\nvalues 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\nsaving time.
\nEach kind above has a corresponding Trunc subclass (listed below) that\nshould typically be used instead of the more verbose equivalent,\ne.g. use TruncYear(...) rather than Trunc(..., kind='year').
The subclasses are all defined as transforms, but they aren't registered with\nany fields, because the obvious lookup names are already reserved by the\nExtract subclasses.
Contoh penggunaan:
\n>>> from datetime import datetime\n>>> from django.db.models import Count, DateTimeField\n>>> from django.db.models.functions import Trunc\n>>> Experiment.objects.create(start_datetime=datetime(2015, 6, 15, 14, 30, 50, 321))\n>>> Experiment.objects.create(start_datetime=datetime(2015, 6, 15, 14, 40, 2, 123))\n>>> Experiment.objects.create(start_datetime=datetime(2015, 12, 25, 10, 5, 27, 999))\n>>> experiments_per_day = Experiment.objects.annotate(\n... start_day=Trunc('start_datetime', 'day', output_field=DateTimeField())\n... ).values('start_day').annotate(experiments=Count('id'))\n>>> for exp in experiments_per_day:\n... print(exp['start_day'], exp['experiments'])\n...\n2015-06-15 00:00:00 2\n2015-12-25 00:00:00 1\n>>> experiments = Experiment.objects.annotate(\n... start_day=Trunc('start_datetime', 'day', output_field=DateTimeField())\n... ).filter(start_day=datetime(2015, 6, 15))\n>>> for exp in experiments:\n... print(exp.start_datetime)\n...\n2015-06-15 14:30:50.000321\n2015-06-15 14:40:02.000123\nDateFieldLink to this heading#Memotong ke tengah malam pada Senin dari minggu.
\nThese are logically equivalent to Trunc('date_field', kind). They truncate\nall parts of the date up to kind which allows grouping or filtering dates\nwith less precision. expression can have an output_field of either\nDateField or DateTimeField.
Since DateFields don't have a time component, only Trunc subclasses\nthat deal with date-parts can be used with DateField:
>>> from datetime import datetime\n>>> from django.db.models import Count\n>>> from django.db.models.functions import TruncMonth, TruncYear\n>>> from django.utils import timezone\n>>> start1 = datetime(2014, 6, 15, 14, 30, 50, 321, tzinfo=timezone.utc)\n>>> start2 = datetime(2015, 6, 15, 14, 40, 2, 123, tzinfo=timezone.utc)\n>>> start3 = datetime(2015, 12, 31, 17, 5, 27, 999, tzinfo=timezone.utc)\n>>> Experiment.objects.create(start_datetime=start1, start_date=start1.date())\n>>> Experiment.objects.create(start_datetime=start2, start_date=start2.date())\n>>> Experiment.objects.create(start_datetime=start3, start_date=start3.date())\n>>> experiments_per_year = Experiment.objects.annotate(\n... year=TruncYear('start_date')).values('year').annotate(\n... experiments=Count('id'))\n>>> for exp in experiments_per_year:\n... print(exp['year'], exp['experiments'])\n...\n2014-01-01 1\n2015-01-01 2\n\n>>> import pytz\n>>> melb = pytz.timezone('Australia/Melbourne')\n>>> experiments_per_month = Experiment.objects.annotate(\n... month=TruncMonth('start_datetime', tzinfo=melb)).values('month').annotate(\n... experiments=Count('id'))\n>>> for exp in experiments_per_month:\n... print(exp['month'], exp['experiments'])\n...\n2015-06-01 00:00:00+10:00 1\n2016-01-01 00:00:00+11:00 1\n2014-06-01 00:00:00+10:00 1\nDateTimeFieldLink to this heading#TruncDate casts expression to a date rather than using the built-in SQL\ntruncate function. It's also registered as a transform on DateTimeField as\n__date.
TruncTime casts expression to a time rather than using the built-in SQL\ntruncate function. It's also registered as a transform on DateTimeField as\n__time.
These are logically equivalent to Trunc('datetime_field', kind). They\ntruncate all parts of the date up to kind and allow grouping or filtering\ndatetimes with less precision. expression must have an output_field of\nDateTimeField.
Contoh penggunaan:
\n>>> from datetime import date, datetime\n>>> from django.db.models import Count\n>>> from django.db.models.functions import (\n... TruncDate, TruncDay, TruncHour, TruncMinute, TruncSecond,\n... )\n>>> from django.utils import timezone\n>>> import pytz\n>>> start1 = datetime(2014, 6, 15, 14, 30, 50, 321, tzinfo=timezone.utc)\n>>> Experiment.objects.create(start_datetime=start1, start_date=start1.date())\n>>> melb = pytz.timezone('Australia/Melbourne')\n>>> Experiment.objects.annotate(\n... date=TruncDate('start_datetime'),\n... day=TruncDay('start_datetime', tzinfo=melb),\n... hour=TruncHour('start_datetime', tzinfo=melb),\n... minute=TruncMinute('start_datetime'),\n... second=TruncSecond('start_datetime'),\n... ).values('date', 'day', 'hour', 'minute', 'second').get()\n{'date': datetime.date(2014, 6, 15),\n 'day': datetime.datetime(2014, 6, 16, 0, 0, tzinfo=<DstTzInfo 'Australia/Melbourne' AEST+10:00:00 STD>),\n 'hour': datetime.datetime(2014, 6, 16, 0, 0, tzinfo=<DstTzInfo 'Australia/Melbourne' AEST+10:00:00 STD>),\n 'minute': 'minute': datetime.datetime(2014, 6, 15, 14, 30, tzinfo=<UTC>),\n 'second': datetime.datetime(2014, 6, 15, 14, 30, 50, tzinfo=<UTC>)\n}\nTimeFieldLink to this heading#These are logically equivalent to Trunc('time_field', kind). They truncate\nall parts of the time up to kind which allows grouping or filtering times\nwith less precision. expression can have an output_field of either\nTimeField or DateTimeField.
Since TimeFields don't have a date component, only Trunc subclasses\nthat deal with time-parts can be used with TimeField:
>>> from datetime import datetime\n>>> from django.db.models import Count, TimeField\n>>> from django.db.models.functions import TruncHour\n>>> from django.utils import timezone\n>>> start1 = datetime(2014, 6, 15, 14, 30, 50, 321, tzinfo=timezone.utc)\n>>> start2 = datetime(2014, 6, 15, 14, 40, 2, 123, tzinfo=timezone.utc)\n>>> start3 = datetime(2015, 12, 31, 17, 5, 27, 999, tzinfo=timezone.utc)\n>>> Experiment.objects.create(start_datetime=start1, start_time=start1.time())\n>>> Experiment.objects.create(start_datetime=start2, start_time=start2.time())\n>>> Experiment.objects.create(start_datetime=start3, start_time=start3.time())\n>>> experiments_per_hour = Experiment.objects.annotate(\n... hour=TruncHour('start_datetime', output_field=TimeField()),\n... ).values('hour').annotate(experiments=Count('id'))\n>>> for exp in experiments_per_hour:\n... print(exp['hour'], exp['experiments'])\n...\n14:00:00 2\n17:00:00 1\n\n>>> import pytz\n>>> melb = pytz.timezone('Australia/Melbourne')\n>>> experiments_per_hour = Experiment.objects.annotate(\n... hour=TruncHour('start_datetime', tzinfo=melb),\n... ).values('hour').annotate(experiments=Count('id'))\n>>> for exp in experiments_per_hour:\n... print(exp['hour'], exp['experiments'])\n...\n2014-06-16 00:00:00+10:00 2\n2016-01-01 04:00:00+11:00 1\nChrLink to this heading#Accepts a numeric field or expression and returns the text representation of\nthe expression as a single character. It works the same as Python's chr()\nfunction.
Like Length, it can be registered as a transform on IntegerField.\nThe default lookup name is chr.
Contoh penggunaan:
\n>>> from django.db.models.functions import Chr\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.filter(name__startswith=Chr(ord('M'))).get()\n>>> print(author.name)\nMargaret Smith\nConcatLink to this heading#Accepts a list of at least two text fields or expressions and returns the\nconcatenated text. Each argument must be of a text or char type. If you want\nto concatenate a TextField() with a CharField(), then be sure to tell\nDjango that the output_field should be a TextField(). Specifying an\noutput_field is also required when concatenating a Value as in the\nexample below.
This function will never have a null result. On backends where a null argument\nresults in the entire expression being null, Django will ensure that each null\npart is converted to an empty string first.
\nContoh penggunaan:
\n>>> # Get the display name as "name (goes_by)"\n>>> from django.db.models import CharField, Value as V\n>>> from django.db.models.functions import Concat\n>>> Author.objects.create(name='Margaret Smith', goes_by='Maggie')\n>>> author = Author.objects.annotate(\n... screen_name=Concat(\n... 'name', V(' ('), 'goes_by', V(')'),\n... output_field=CharField()\n... )\n... ).get()\n>>> print(author.screen_name)\nMargaret Smith (Maggie)\nLeftLink to this heading#Mengembalikan length karakter pertama dari bidang teks atau pernyataan yang diberikan.
Contoh penggunaan:
\n>>> from django.db.models.functions import Left\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.annotate(first_initial=Left('name', 1)).get()\n>>> print(author.first_initial)\nM\nLengthLink to this heading#Accepts a single text field or expression and returns the number of characters\nthe value has. If the expression is null, then the length will also be null.
\nContoh penggunaan:
\n>>> # Get the length of the name and goes_by fields\n>>> from django.db.models.functions import Length\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.annotate(\n... name_length=Length('name'),\n... goes_by_length=Length('goes_by')).get()\n>>> print(author.name_length, author.goes_by_length)\n(14, None)\nItu dapat juga didaftarkan sebagai sebuah perubahan. Sebagai contoh:
\n>>> from django.db.models import CharField\n>>> from django.db.models.functions import Length\n>>> CharField.register_lookup(Length)\n>>> # Get authors whose name is longer than 7 characters\n>>> authors = Author.objects.filter(name__length__gt=7)\nLowerLink to this heading#Menerima bidang teks tunggal atau pernyataan dan mengembalikan perwakilan huruf kecil.
\nItu dapat juga didaftarkan sebagai sebuah perubahan seperti digambarkan dalam Length.
Contoh penggunaan:
\n>>> from django.db.models.functions import Lower\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.annotate(name_lower=Lower('name')).get()\n>>> print(author.name_lower)\nmargaret smith\nLPadLink to this heading#Returns the value of the given text field or expression padded on the left side\nwith fill_text so that the resulting value is length characters long.\nThe default fill_text is a space.
Contoh penggunaan:
\n>>> from django.db.models import Value\n>>> from django.db.models.functions import LPad\n>>> Author.objects.create(name='John', alias='j')\n>>> Author.objects.update(name=LPad('name', 8, Value('abc')))\n1\n>>> print(Author.objects.get(alias='j').name)\nabcaJohn\nLTrimLink to this heading#Mirip pada Trim, tetapi hanya memindahkan spasi awal.
OrdLink to this heading#Accepts a single text field or expression and returns the Unicode code point\nvalue for the first character of that expression. It works similar to Python's\nord() function, but an exception isn't raised if the expression is more\nthan one character long.
It can also be registered as a transform as described in Length.\nThe default lookup name is ord.
Contoh penggunaan:
\n>>> from django.db.models.functions import Ord\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.annotate(name_code_point=Ord('name')).get()\n>>> print(author.name_code_point)\n77\nRepeatLink to this heading#Mengembalikan nilai dari bidang teks diberikan atau pernyataan diulang number kali.
Contoh penggunaan:
\n>>> from django.db.models.functions import Repeat\n>>> Author.objects.create(name='John', alias='j')\n>>> Author.objects.update(name=Repeat('name', 3))\n1\n>>> print(Author.objects.get(alias='j').name)\nJohnJohnJohn\nReplaceLink to this heading#Replaces all occurrences of text with replacement in expression.\nThe default replacement text is the empty string. The arguments to the function\nare case-sensitive.
Contoh penggunaan:
\n>>> from django.db.models import Value\n>>> from django.db.models.functions import Replace\n>>> Author.objects.create(name='Margaret Johnson')\n>>> Author.objects.create(name='Margaret Smith')\n>>> Author.objects.update(name=Replace('name', Value('Margaret'), Value('Margareth')))\n2\n>>> Author.objects.values('name')\n<QuerySet [{'name': 'Margareth Johnson'}, {'name': 'Margareth Smith'}]>\nRightLink to this heading#Mengembalikan length karakter terakhir dari bidang teks atau pernyataan yang diberikan.
Contoh penggunaan:
\n>>> from django.db.models.functions import Right\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.annotate(last_letter=Right('name', 1)).get()\n>>> print(author.last_letter)\nh\nRPadLink to this heading#Mirip pada LPad, tetapi menambahkan pada sisi kanan.
RTrimLink to this heading#Mirip pada Trim, namum memindahkan hanya spasi tambahan.
StrIndexLink to this heading#Returns a positive integer corresponding to the 1-indexed position of the first\noccurrence of substring inside string, or 0 if substring is not\nfound.
Contoh penggunaan:
\n>>> from django.db.models import Value as V\n>>> from django.db.models.functions import StrIndex\n>>> Author.objects.create(name='Margaret Smith')\n>>> Author.objects.create(name='Smith, Margaret')\n>>> Author.objects.create(name='Margaret Jackson')\n>>> Author.objects.filter(name='Margaret Jackson').annotate(\n... smith_index=StrIndex('name', V('Smith'))\n... ).get().smith_index\n0\n>>> authors = Author.objects.annotate(\n... smith_index=StrIndex('name', V('Smith'))\n... ).filter(smith_index__gt=0)\n<QuerySet [<Author: Margaret Smith>, <Author: Smith, Margaret>]>\nSubstrLink to this heading#Returns a substring of length length from the field or expression starting\nat position pos. The position is 1-indexed, so the position must be greater\nthan 0. If length is None, then the rest of the string will be returned.
Contoh penggunaan:
\n>>> # Set the alias to the first 5 characters of the name as lowercase\n>>> from django.db.models.functions import Lower, Substr\n>>> Author.objects.create(name='Margaret Smith')\n>>> Author.objects.update(alias=Lower(Substr('name', 1, 5)))\n1\n>>> print(Author.objects.get(name='Margaret Smith').alias)\nmarga\nTrimLink to this heading#Returns the value of the given text field or expression with leading and\ntrailing spaces removed.
\nContoh penggunaan:
\n>>> from django.db.models.functions import Trim\n>>> Author.objects.create(name=' John ', alias='j')\n>>> Author.objects.update(name=Trim('name'))\n1\n>>> print(Author.objects.get(alias='j').name)\nJohn\nUpperLink to this heading#Accepts a single text field or expression and returns the uppercase\nrepresentation.
\nItu dapat juga didaftarkan sebagai sebuah perubahan seperti digambarkan dalam Length.
Contoh penggunaan:
\n>>> from django.db.models.functions import Upper\n>>> Author.objects.create(name='Margaret Smith')\n>>> author = Author.objects.annotate(name_upper=Upper('name')).get()\n>>> print(author.name_upper)\nMARGARET SMITH\nThere are a number of functions to use in a\nWindow expression for computing the rank\nof elements or the Ntile of some rows.
CumeDistLink to this heading#Calculates the cumulative distribution of a value within a window or partition.\nThe cumulative distribution is defined as the number of rows preceding or\npeered with the current row divided by the total number of rows in the frame.
\nDenseRankLink to this heading#Equivalent to Rank but does not have gaps.
FirstValueLink to this heading#Returns the value evaluated at the row that's the first row of the window\nframe, or None if no such value exists.
LagLink to this heading#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\nonly validated by the database and not in Python.
LastValueLink to this heading#Dibandingkan pada FirstValue, itu menghitung nilai terakhir dalam klausa kerangka yang diberikan.
LeadLink to this heading#Calculates the leading value in a given frame. Both\noffset and default are evaluated with respect to the current row.
default must have the same type as the expression, however, this is\nonly validated by the database and not in Python.
NthValueLink to this heading#Computes the row relative to the offset nth (must be a positive value)\nwithin the window. Returns None if no row exists.
Some databases may handle a nonexistent nth-value differently. For example,\nOracle returns an empty string rather than None for character-based\nexpressions. Django doesn't do any conversions in these cases.
NtileLink to this heading#Calculates a partition for each of the rows in the frame clause, distributing\nnumbers as evenly as possible between 1 and num_buckets. If the rows don't\ndivide evenly into a number of buckets, one or more buckets will be represented\nmore frequently.
PercentRankLink to this heading#Computes the percentile rank of the rows in the frame clause. This\ncomputation is equivalent to evaluating:
\n(rank - 1) / (total rows - 1)\nTabel berikut menjelaskan perhitungan untuk peringkat perseratus dari sebuah baris:
\nBaris # | \nNilai | \nPeringkat | \nPerhitungan | \nPeringkat Persen | \n
|---|---|---|---|---|
1 | \n15 | \n1 | \n(1-1)/(7-1) | \n0.0000 | \n
2 | \n20 | \n2 | \n(2-1)/(7-1) | \n0.1666 | \n
3 | \n20 | \n2 | \n(2-1)/(7-1) | \n0.1666 | \n
4 | \n20 | \n2 | \n(2-1)/(7-1) | \n0.1666 | \n
5 | \n30 | \n5 | \n(5-1)/(7-1) | \n0.6666 | \n
6 | \n30 | \n5 | \n(5-1)/(7-1) | \n0.6666 | \n
7 | \n40 | \n7 | \n(7-1)/(7-1) | \n1.0000 | \n
RankLink to this heading#Comparable to RowNumber, this function ranks rows in the window. The\ncomputed rank contains gaps. Use DenseRank to compute rank without\ngaps.
RowNumberLink to this heading#Computes the row number according to the ordering of either the frame clause\nor the ordering of the whole query if there is no partitioning of the\nwindow frame.
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