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sql-functions-aggs.md

sql-functions-aggs.md 23 KB
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Aggregate functions [sql-functions-aggs]

Functions for computing a single result from a set of input values. Elasticsearch SQL supports aggregate functions only alongside grouping (implicit or explicit).

General purpose [sql-functions-aggs-general]

AVG [sql-functions-aggs-avg]

AVG(numeric_field) <1>

Input:

  1. numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description: Returns the Average (arithmetic mean) of input values.

SELECT AVG(salary) AS avg FROM emp;

      avg
---------------
48248.55

SELECT AVG(salary / 12.0) AS avg FROM emp;

      avg
---------------
4020.7125

COUNT [sql-functions-aggs-count]

COUNT(expression) <1>

Input:

  1. a field name, wildcard (*) or any numeric value. For COUNT(*) or COUNT(<literal>), all values are considered, including null or missing ones. For COUNT(<field_name>), null values are not considered.

Output: numeric value

Description: Returns the total number (count) of input values.

SELECT COUNT(*) AS count FROM emp;

     count
---------------
100

COUNT(ALL) [sql-functions-aggs-count-all]

COUNT(ALL field_name) <1>

Input:

  1. a field name. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: numeric value

Description: Returns the total number (count) of all non-null input values. COUNT(<field_name>) and COUNT(ALL <field_name>) are equivalent.

SELECT COUNT(ALL last_name) AS count_all, COUNT(DISTINCT last_name) count_distinct FROM emp;

   count_all   |  count_distinct
---------------+------------------
100            |96

SELECT COUNT(ALL CASE WHEN languages IS NULL THEN -1 ELSE languages END) AS count_all, COUNT(DISTINCT CASE WHEN languages IS NULL THEN -1 ELSE languages END) count_distinct FROM emp;

   count_all   |  count_distinct
---------------+---------------
100            |6

COUNT(DISTINCT) [sql-functions-aggs-count-distinct]

COUNT(DISTINCT field_name) <1>

Input:

  1. a field name

Output: numeric value. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Description: Returns the total number of distinct non-null values in input values.

SELECT COUNT(DISTINCT hire_date) unique_hires, COUNT(hire_date) AS hires FROM emp;

  unique_hires  |     hires
----------------+---------------
99              |100

SELECT COUNT(DISTINCT DATE_TRUNC('YEAR', hire_date)) unique_hires, COUNT(DATE_TRUNC('YEAR', hire_date)) AS hires FROM emp;

 unique_hires  |     hires
---------------+---------------
14             |100

FIRST/FIRST_VALUE [sql-functions-aggs-first]

FIRST(
    field_name               <1>
    [, ordering_field_name]) <2>

Input:

  1. target field for the aggregation
  2. optional field used for ordering

Output: same type as the input

Description: Returns the first non-null value (if such exists) of the field_name input column sorted by the ordering_field_name column. If ordering_field_name is not provided, only the field_name column is used for the sorting. E.g.:

a b
100 1
200 1
1 2
2 2
10 null
20 null
null null 
SELECT FIRST(a) FROM t

will result in:

FIRST(a)
1

and

SELECT FIRST(a, b) FROM t

will result in:

FIRST(a, b)
100 
SELECT FIRST(first_name) FROM emp;

   FIRST(first_name)
--------------------
Alejandro

SELECT gender, FIRST(first_name) FROM emp GROUP BY gender ORDER BY gender;

   gender   |   FIRST(first_name)
------------+--------------------
null        |   Berni
F           |   Alejandro
M           |   Amabile

SELECT FIRST(first_name, birth_date) FROM emp;

   FIRST(first_name, birth_date)
--------------------------------
Remzi

SELECT gender, FIRST(first_name, birth_date) FROM emp GROUP BY gender ORDER BY gender;

    gender    |   FIRST(first_name, birth_date)
--------------+--------------------------------
null          |   Lillian
F             |   Sumant
M             |   Remzi

FIRST_VALUE is a name alias and can be used instead of FIRST, e.g.:

SELECT gender, FIRST_VALUE(first_name, birth_date) FROM emp GROUP BY gender ORDER BY gender;

    gender    |   FIRST_VALUE(first_name, birth_date)
--------------+--------------------------------------
null          |   Lillian
F             |   Sumant
M             |   Remzi

SELECT gender, FIRST_VALUE(SUBSTRING(first_name, 2, 6), birth_date) AS "first" FROM emp GROUP BY gender ORDER BY gender;

    gender     |     first
---------------+---------------
null           |illian
F              |umant
M              |emzi

::::{note} FIRST cannot be used in a HAVING clause. ::::

::::{note} FIRST cannot be used with columns of type text unless the field is also saved as a keyword. ::::

LAST/LAST_VALUE [sql-functions-aggs-last]

LAST(
    field_name               <1>
    [, ordering_field_name]) <2>

Input:

  1. target field for the aggregation
  2. optional field used for ordering

Output: same type as the input

Description: It’s the inverse of FIRST/FIRST_VALUE. Returns the last non-null value (if such exists) of the field_name input column sorted descending by the ordering_field_name column. If ordering_field_name is not provided, only the field_name column is used for the sorting. E.g.:

a b
10 1
20 1
1 2
2 2
100 null
200 null
null null 
SELECT LAST(a) FROM t

will result in:

LAST(a)
200

and

SELECT LAST(a, b) FROM t

will result in:

LAST(a, b)
2 
SELECT LAST(first_name) FROM emp;

   LAST(first_name)
-------------------
Zvonko

SELECT gender, LAST(first_name) FROM emp GROUP BY gender ORDER BY gender;

   gender   |   LAST(first_name)
------------+-------------------
null        |   Patricio
F           |   Xinglin
M           |   Zvonko

SELECT LAST(first_name, birth_date) FROM emp;

   LAST(first_name, birth_date)
-------------------------------
Hilari

SELECT gender, LAST(first_name, birth_date) FROM emp GROUP BY gender ORDER BY gender;

   gender  |   LAST(first_name, birth_date)
-----------+-------------------------------
null       |   Eberhardt
F          |   Valdiodio
M          |   Hilari

LAST_VALUE is a name alias and can be used instead of LAST, e.g.:

SELECT gender, LAST_VALUE(first_name, birth_date) FROM emp GROUP BY gender ORDER BY gender;

   gender  |   LAST_VALUE(first_name, birth_date)
-----------+-------------------------------------
null       |   Eberhardt
F          |   Valdiodio
M          |   Hilari

SELECT gender, LAST_VALUE(SUBSTRING(first_name, 3, 8), birth_date) AS "last" FROM emp GROUP BY gender ORDER BY gender;

    gender     |     last
---------------+---------------
null           |erhardt
F              |ldiodio
M              |lari

::::{note} LAST cannot be used in HAVING clause. ::::

::::{note} LAST cannot be used with columns of type text unless the field is also saved as a keyword. ::::

MAX [sql-functions-aggs-max]

MAX(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: same type as the input

Description: Returns the maximum value across input values in the field field_name.

SELECT MAX(salary) AS max FROM emp;

      max
---------------
74999

SELECT MAX(ABS(salary / -12.0)) AS max FROM emp;

       max
-----------------
6249.916666666667

::::{note} MAX on a field of type text or keyword is translated into LAST/LAST_VALUE and therefore, it cannot be used in HAVING clause. ::::

MIN [sql-functions-aggs-min]

MIN(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: same type as the input

Description: Returns the minimum value across input values in the field field_name.

SELECT MIN(salary) AS min FROM emp;

      min
---------------
25324

::::{note} MIN on a field of type text or keyword is translated into FIRST/FIRST_VALUE and therefore, it cannot be used in HAVING clause. ::::

SUM [sql-functions-aggs-sum]

SUM(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: bigint for integer input, double for floating points

Description: Returns the sum of input values in the field field_name.

SELECT SUM(salary) AS sum FROM emp;

      sum
---------------
4824855

SELECT ROUND(SUM(salary / 12.0), 1) AS sum FROM emp;

      sum
---------------
402071.3

Statistics [sql-functions-aggs-statistics]

KURTOSIS [sql-functions-aggs-kurtosis]

KURTOSIS(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Quantify the shape of the distribution of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, KURTOSIS(salary) AS k FROM emp;

      min      |      max      |        k
---------------+---------------+------------------
25324          |74999          |2.0444718929142986

::::{note} KURTOSIS cannot be used on top of scalar functions or operators but only directly on a field. So, for example, the following is not allowed and an error is returned:

 SELECT KURTOSIS(salary / 12.0), gender FROM emp GROUP BY gender

::::

MAD [sql-functions-aggs-mad]

MAD(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Measure the variability of the input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, AVG(salary) AS avg, MAD(salary) AS mad FROM emp;

      min      |      max      |      avg      |      mad
---------------+---------------+---------------+---------------
25324          |74999          |48248.55       |10096.5

SELECT MIN(salary / 12.0) AS min, MAX(salary / 12.0) AS max, AVG(salary/ 12.0) AS avg, MAD(salary / 12.0) AS mad FROM emp;

       min        |       max       |      avg      |       mad
------------------+-----------------+---------------+-----------------
2110.3333333333335|6249.916666666667|4020.7125      |841.3750000000002

PERCENTILE [sql-functions-aggs-percentile]

PERCENTILE(
    field_name,         <1>
    percentile[,        <2>
    method[,            <3>
    method_parameter]]) <4>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.
  2. a numeric expression (must be a constant and not based on a field). If null, the function returns null.
  3. optional string literal for the percentile algorithm. Possible values: tdigest or hdr. Defaults to tdigest.
  4. optional numeric literal that configures the percentile algorithm. Configures compression for tdigest or number_of_significant_value_digits for hdr. The default is the same as that of the backing algorithm.

Output: double numeric value

Description:

Returns the nth percentile (represented by numeric_exp parameter) of input values in the field field_name.

SELECT languages, PERCENTILE(salary, 95) AS "95th" FROM emp
       GROUP BY languages;

   languages   |      95th
---------------+-----------------
null           |74482.4
1              |71122.8
2              |70271.4
3              |71926.0
4              |69352.15
5              |56371.0

SELECT languages, PERCENTILE(salary / 12.0, 95) AS "95th" FROM emp
       GROUP BY languages;

   languages   |       95th
---------------+------------------
null           |6206.866666666667
1              |5926.9
2              |5855.949999999999
3              |5993.833333333333
4              |5779.345833333333
5              |4697.583333333333

SELECT
    languages,
    PERCENTILE(salary, 97.3, 'tdigest', 100.0) AS "97.3_TDigest",
    PERCENTILE(salary, 97.3, 'hdr', 3) AS "97.3_HDR"
FROM emp
GROUP BY languages;

   languages   | 97.3_TDigest    |   97.3_HDR
---------------+-----------------+---------------
null           |74720.036        |74992.0
1              |72316.132        |73712.0
2              |71792.436        |69936.0
3              |73326.23999999999|74992.0
4              |71753.281        |74608.0
5              |61176.16000000001|56368.0

PERCENTILE_RANK [sql-functions-aggs-percentile-rank]

PERCENTILE_RANK(
    field_name,         <1>
    value[,             <2>
    method[,            <3>
    method_parameter]]) <4>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.
  2. a numeric expression (must be a constant and not based on a field). If null, the function returns null.
  3. optional string literal for the percentile algorithm. Possible values: tdigest or hdr. Defaults to tdigest.
  4. optional numeric literal that configures the percentile algorithm. Configures compression for tdigest or number_of_significant_value_digits for hdr. The default is the same as that of the backing algorithm.

Output: double numeric value

Description:

Returns the nth percentile rank (represented by numeric_exp parameter) of input values in the field field_name.

SELECT languages, PERCENTILE_RANK(salary, 65000) AS rank FROM emp GROUP BY languages;

   languages   |      rank
---------------+-----------------
null           |73.65766569962062
1              |73.7291625157734
2              |88.88005607010643
3              |79.43662623295829
4              |85.70446389643493
5              |96.79075152940749

SELECT languages, PERCENTILE_RANK(salary/12, 5000) AS rank FROM emp GROUP BY languages;

   languages   |       rank
---------------+------------------
null           |66.91240875912409
1              |66.70766707667076
2              |84.13266895048271
3              |61.052992625621684
4              |76.55646443990001
5              |94.00696864111498

SELECT
    languages,
    ROUND(PERCENTILE_RANK(salary, 65000, 'tdigest', 100.0), 2) AS "rank_TDigest",
    ROUND(PERCENTILE_RANK(salary, 65000, 'hdr', 3), 2) AS "rank_HDR"
FROM emp
GROUP BY languages;

   languages   | rank_TDigest  |   rank_HDR
---------------+---------------+---------------
null           |73.66          |80.0
1              |73.73          |73.33
2              |88.88          |89.47
3              |79.44          |76.47
4              |85.7           |83.33
5              |96.79          |95.24

SKEWNESS [sql-functions-aggs-skewness]

SKEWNESS(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Quantify the asymmetric distribution of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, SKEWNESS(salary) AS s FROM emp;

      min      |      max      |        s
---------------+---------------+------------------
25324          |74999          |0.2707722118423227

::::{note} SKEWNESS cannot be used on top of scalar functions but only directly on a field. So, for example, the following is not allowed and an error is returned:

 SELECT SKEWNESS(ROUND(salary / 12.0, 2), gender FROM emp GROUP BY gender

::::

STDDEV_POP [sql-functions-aggs-stddev-pop]

STDDEV_POP(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Returns the population standard deviation of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, STDDEV_POP(salary) AS stddev FROM emp;

      min      |      max      |      stddev
---------------+---------------+------------------
25324          |74999          |13765.125502787832

SELECT MIN(salary / 12.0) AS min, MAX(salary / 12.0) AS max, STDDEV_POP(salary / 12.0) AS stddev FROM emp;

       min        |       max       |     stddev
------------------+-----------------+-----------------
2110.3333333333335|6249.916666666667|1147.093791898986

STDDEV_SAMP [sql-functions-aggs-stddev-samp]

STDDEV_SAMP(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Returns the sample standard deviation of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, STDDEV_SAMP(salary) AS stddev FROM emp;

      min      |      max      |      stddev
---------------+---------------+------------------
25324          |74999          |13834.471662090747

SELECT MIN(salary / 12.0) AS min, MAX(salary / 12.0) AS max, STDDEV_SAMP(salary / 12.0) AS stddev FROM emp;

       min        |       max       |     stddev
------------------+-----------------+-----------------
2110.3333333333335|6249.916666666667|1152.872638507562

SUM_OF_SQUARES [sql-functions-aggs-sum-squares]

SUM_OF_SQUARES(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Returns the sum of squares of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, SUM_OF_SQUARES(salary) AS sumsq
       FROM emp;

      min      |      max      |     sumsq
---------------+---------------+----------------
25324          |74999          |2.51740125721E11

SELECT MIN(salary / 24.0) AS min, MAX(salary / 24.0) AS max, SUM_OF_SQUARES(salary / 24.0) AS sumsq FROM emp;

       min        |       max        |       sumsq
------------------+------------------+-------------------
1055.1666666666667|3124.9583333333335|4.370488293767361E8

VAR_POP [sql-functions-aggs-var-pop]

VAR_POP(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Returns the population variance of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, VAR_POP(salary) AS varpop FROM emp;

      min      |      max      |     varpop
---------------+---------------+----------------
25324          |74999          |1.894786801075E8

SELECT MIN(salary / 24.0) AS min, MAX(salary / 24.0) AS max, VAR_POP(salary / 24.0) AS varpop FROM emp;

       min        |       max        |      varpop
------------------+------------------+------------------
1055.1666666666667|3124.9583333333335|328956.04185329855

VAR_SAMP [sql-functions-aggs-var-samp]

VAR_SAMP(field_name) <1>

Input:

  1. a numeric field. If this field contains only null values, the function returns null. Otherwise, the function ignores null values in this field.

Output: double numeric value

Description:

Returns the sample variance of input values in the field field_name.

SELECT MIN(salary) AS min, MAX(salary) AS max, VAR_SAMP(salary) AS varsamp FROM emp;

      min      |      max      |     varsamp
---------------+---------------+----------------
25324          |74999          |1.913926061691E8

SELECT MIN(salary / 24.0) AS min, MAX(salary / 24.0) AS max, VAR_SAMP(salary / 24.0) AS varsamp FROM emp;

       min        |       max        |     varsamp
------------------+------------------+----------------
1055.1666666666667|3124.9583333333335|332278.830154847