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Implementation of Hypothetical-Set Aggregate Functions#9035

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sim1984:hypotset-agg-functions
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Implementation of Hypothetical-Set Aggregate Functions#9035
sim1984 wants to merge 3 commits into
FirebirdSQL:masterfrom
sim1984:hypotset-agg-functions

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@sim1984 sim1984 commented May 22, 2026 •
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Hypothetical-Set Aggregate Functions

Hypothetical set functions include ranking and rank distribution functions, which you are already familiar with as window functions, but they are applied to groups to enter values ​​in hypothetical form.

There are two sorted set ranking functions: RANK and DENSE_RANK. There are also two sorted set rank distribution functions: PERCENT_RANK and CUME_DIST. Window functions and ordered set functions differ in the way they order. The former order within a window, while the latter order within a group.

Syntax of aggregate functions of a hypothetical set:

<hypothetical-set-agg-function> ::=
      RANK(<args>) WITHIN GROUP (ORDER BY <sorted_args>)
    | DENSE_RANK(<args>) WITHIN GROUP (ORDER BY <sorted_args>)
    | PERCENT_RANK(<args>) WITHIN GROUP (ORDER BY <sorted_args>)
    | CUME_DIST(<args>) WITHIN GROUP (ORDER BY <sorted_args>)

Each of the "hypothetical-set" aggregates is associated with a window function of the same name. In each case, the aggregate's result is the value that the associated window function would have returned for the "hypothetical" row constructed from args, if such a row had been added to the sorted group of rows represented by the sorted_args. For each of these functions, the list of direct arguments given in args must match the number and types of the aggregated arguments given in sorted_args. Unlike most built-in aggregates, these aggregates are not strict, that is they do not drop input rows containing NULLs. NULL values sort according to the rule specified in the ORDER BY clause.

The values ​​of the input arguments args must be constant within each group.

An example of using hypothetical set functions without grouping:

SELECT
  RANK(35500) WITHIN GROUP(ORDER BY E.SALARY) AS R1,
  DENSE_RANK(35500) WITHIN GROUP(ORDER BY E.SALARY) AS R2,
  PERCENT_RANK(35500) WITHIN GROUP(ORDER BY E.SALARY) AS PR,
  CUME_DIST(35500) WITHIN GROUP(ORDER BY E.SALARY) AS CD
FROM EMPLOYEE E;
                   R1                    R2                      PR                      CD
===================== ===================== ======================= =======================
                    9                     8      0.1904761904761905      0.2093023255813954

An example of using hypothetical set functions with grouping:

SELECT
  E.JOB_COUNTRY,
  RANK(35500) WITHIN GROUP(ORDER BY E.SALARY) AS R1,
  DENSE_RANK(35500) WITHIN GROUP(ORDER BY E.SALARY) AS R2,
  PERCENT_RANK(35500) WITHIN GROUP(ORDER BY E.SALARY) AS PR,
  CUME_DIST(35500) WITHIN GROUP(ORDER BY E.SALARY) AS CD
FROM EMPLOYEE E
GROUP BY E.JOB_COUNTRY;
JOB_COUNTRY                        R1                    R2                      PR                      CD
=============== ===================== ===================== ======================= =======================
Canada                              1                     1       0.000000000000000      0.5000000000000000
England                             3                     3      0.6666666666666666      0.7500000000000000
France                              1                     1       0.000000000000000      0.5000000000000000
Italy                               2                     2       1.000000000000000       1.000000000000000
Japan                               1                     1       0.000000000000000      0.3333333333333333
Switzerland                         1                     1       0.000000000000000      0.5000000000000000
USA                                 6                     5      0.1515151515151515      0.1764705882352941

An example of using hypothetical functions with two arguments:

SELECT
  RANK('England', 35500) WITHIN GROUP(ORDER BY E.JOB_COUNTRY, E.SALARY) AS R1,
  DENSE_RANK('England', 35500) WITHIN GROUP(ORDER BY E.JOB_COUNTRY, E.SALARY) AS R2,
  PERCENT_RANK('England', 35500) WITHIN GROUP(ORDER BY E.JOB_COUNTRY, E.SALARY) AS PR,
  CUME_DIST('England', 35500) WITHIN GROUP(ORDER BY E.JOB_COUNTRY, E.SALARY) AS CD
FROM EMPLOYEE E;
                   R1                    R2                      PR                      CD
===================== ===================== ======================= =======================
                    4                     4     0.07142857142857142     0.09302325581395349

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sim1984 commented May 22, 2026

This PR completely closes the issue #7632
All standard functions with the WITHIN GROUP clause are implemented.

@sim1984 sim1984 mentioned this pull request May 22, 2026
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