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Fungsi pengumpulan khusus PostgreSQL

Fungsi-fungsi ini digambarkan lebih rinci di PostgreSQL docs.

Fungsi pengumpulan tujuan-umum

ArrayAgg

class ArrayAgg(expression, distinct=False, filter=None, **extra)

Mengembalikan daftar nilai, termasuk null, disambungkan kedalam larik.

distinct

An optional boolean argument that determines if array values will be distinct. Defaults to False.

BitAnd

class BitAnd(expression, filter=None, **extra)

Mengembalikan sebuah int dari bitwise AND dari semua nilai-nilai masukan bukan-null, atau None jika semua nilai-nilai adalah null.

BitOr

class BitOr(expression, filter=None, **extra)

Mengembalikan sebuah int dari bitwise OR dari semua nilai-nilai masukan bukan-null, atau None jika semua nilai-nilai adalah null.

BoolAnd

class BoolAnd(expression, filter=None, **extra)

Mengembalikan True, jika semua nilai-nilai masukan adalah true, None jika semua nilai-nilai adalah null jika tidak ada nilai, jika tidak False.

BoolOr

class BoolOr(expression, filter=None, **extra)

Mengembalikan True, jika setidaknya satu nilai masukan adalah true, None jika semua nilai-nilai adalah null atau, j jika tidak ada nilai, jika tidak False.

JSONBAgg

class JSONBAgg(expressions, filter=None, **extra)

Returns the input values as a JSON array. Requires PostgreSQL ≥ 9.5.

StringAgg

class StringAgg(expression, delimiter, distinct=False, filter=None)

Mengembalikan nilai-nilai masukan digabungkan kedalam string, dipisah berdasarkan string delimiter

delimiter

Diwajibkan argumen. Butuh berupa sebuah string.

distinct

An optional boolean argument that determines if concatenated values will be distinct. Defaults to False.

Fungsi-fungsi pengumpulan untuk statistik

y dan x

The arguments y and x for all these functions can be the name of a field or an expression returning a numeric data. Both are required.

Corr

class Corr(y, x, filter=None)

Returns the correlation coefficient as a float, or None if there aren't any matching rows.

CovarPop

class CovarPop(y, x, sample=False, filter=None)

Returns the population covariance as a float, or None if there aren't any matching rows.

Mempunyai satu argumen pilihan:

sample

By default CovarPop returns the general population covariance. However, if sample=True, the return value will be the sample population covariance.

RegrAvgX

class RegrAvgX(y, x, filter=None)

Returns the average of the independent variable (sum(x)/N) as a float, or None if there aren't any matching rows.

RegrAvgY

class RegrAvgY(y, x, filter=None)

Returns the average of the dependent variable (sum(y)/N) as a float, or None if there aren't any matching rows.

RegrCount

class RegrCount(y, x, filter=None)

Returns an int of the number of input rows in which both expressions are not null.

RegrIntercept

class RegrIntercept(y, x, filter=None)

Returns the y-intercept of the least-squares-fit linear equation determined by the (x, y) pairs as a float, or None if there aren't any matching rows.

RegrR2

class RegrR2(y, x, filter=None)

Returns the square of the correlation coefficient as a float, or None if there aren't any matching rows.

RegrSlope

class RegrSlope(y, x, filter=None)

Returns the slope of the least-squares-fit linear equation determined by the (x, y) pairs as a float, or None if there aren't any matching rows.

RegrSXX

class RegrSXX(y, x, filter=None)

Returns sum(x^2) - sum(x)^2/N ("sum of squares" of the independent variable) as a float, or None if there aren't any matching rows.

RegrSXY

class RegrSXY(y, x, filter=None)

Returns sum(x*y) - sum(x) * sum(y)/N ("sum of products" of independent times dependent variable) as a float, or None if there aren't any matching rows.

RegrSYY

class RegrSYY(y, x, filter=None)

Returns sum(y^2) - sum(y)^2/N ("sum of squares" of the dependent variable) as a float, or None if there aren't any matching rows.

Contoh penggunaan

Kami akan gunakan tabel contoh ini

Code
| FIELD1 | FIELD2 | FIELD3 |
|--------|--------|--------|
|    foo |      1 |     13 |
|    bar |      2 | (null) |
|   test |      3 |     13 |

Ini adalah beberapa contoh dari beberapa fungsi-fungsi pengumpulan tujuan-umum:

Code
>>> TestModel.objects.aggregate(result=StringAgg('field1', delimiter=';'))
{'result': 'foo;bar;test'}
>>> TestModel.objects.aggregate(result=ArrayAgg('field2'))
{'result': [1, 2, 3]}
>>> TestModel.objects.aggregate(result=ArrayAgg('field1'))
{'result': ['foo', 'bar', 'test']}

Contoh selanjutnya menunjukkan penggunaan dari fungsi-fungsi pengumpulan statistik. Jalur pokok akan tidak digambarkan (anda dapat membaca tentang ini, sebagai contoh, pada wikipedia):

Code
>>> TestModel.objects.aggregate(count=RegrCount(y='field3', x='field2'))
{'count': 2}
>>> TestModel.objects.aggregate(avgx=RegrAvgX(y='field3', x='field2'),
...                             avgy=RegrAvgY(y='field3', x='field2'))
{'avgx': 2, 'avgy': 13}
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