Help Center/ GaussDB(DWS)/ Tool Guide/ DSC/ Oracle Syntax Migration/ System Functions/ Analytical Functions
Updated on 2024-12-09 GMT+08:00
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Analytical Functions

Analytical functions compute an aggregate value based on a group of rows. They differ from aggregate functions in that they return multiple rows for each group. Analytical functions are commonly used to compute cumulative, moving, centered, and reporting aggregates. DSC supports analytical functions including the RATIO_TO_REPORT function.

Input - Analytical Functions

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SELECT empno, ename,  deptno
  , COUNT(*) OVER() AS cnt
  , AVG(DISTINCT empno) OVER (PARTITION BY deptno) AS cnt_dst
  FROM emp
ORDER BY empno;

Output

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WITH aggDistQuery1 AS (
     SELECT
               deptno
               ,AVG (
                    DISTINCT empno
               ) aggDistAlias1
          FROM
               emp
          GROUP BY
               deptno
) SELECT
          empno
          ,ename
          ,deptno
          ,COUNT( * ) OVER( ) AS cnt
          ,(
               SELECT
                         aggDistAlias1
                    FROM
                         aggDistQuery1
                    WHERE
                         deptno = MigTblAlias.deptno
          ) AS cnt_dst
     FROM
          emp MigTblAlias
     ORDER BY
         empno
;

RATIO_TO_REPORT

RATIO_TO_REPORT is an analytic function which returns the proportion of a value to a group of values.

Input - RATIO_TO_REPORT

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SELECT last_name, salary
           , RATIO_TO_REPORT(salary) OVER () AS rr
  FROM employees
WHERE job_id = 'PU_CLERK';

Output

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SELECT last_name, salary
     , salary / NULLIF( SUM (salary) OVER( ), 0 ) AS rr
  FROM employees
WHERE job_id = 'PU_CLERK';

Input - RATIO_TO_REPORT with AGGREGATE column in SELECT

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SELECT
          Ename
          ,Deptno
          ,Empno
          ,SUM (salary)
          ,RATIO_TO_REPORT (
               COUNT( DISTINCT Salary )
          ) OVER( PARTITION BY Deptno ) RATIO
     FROM
          emp1
     ORDER BY
          Ename
          ,Deptno
          ,Empno
;

Output

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SELECT
          Ename
          ,Deptno
          ,Empno
          ,SUM (salary)
          ,COUNT( DISTINCT Salary ) / NULLIF( SUM ( COUNT( DISTINCT Salary ) ) OVER( PARTITION BY Deptno ) ,0 ) RATIO
     FROM
          emp1
     ORDER BY
          Ename
          ,Deptno
          ,Empno
;

Input - RATIO_TO_REPORT with the AGGREGATE column using extending grouping feature but OUNT (Salary) in the RATIO TO REPORT column is not present in SELECT

Use the extendedGroupByClause configuration parameter to configure migration of the extended GROUP BY clause.

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SELECT
          Ename
          ,Deptno
          ,Empno
          ,SUM (salary)
          ,RATIO_TO_REPORT (
               COUNT( Salary )
          ) OVER( PARTITION BY Deptno ) RATIO
     FROM
          emp1
     GROUP BY
          GROUPING SETS (
               Ename
               ,Deptno
               ,Empno
          )
     ORDER BY
          Ename
          ,Deptno
          ,Empno
;

Output

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SELECT
          Ename
          ,Deptno
          ,Empno
          ,ColumnAlias1
          ,aggColumnalias1 / NULLIF( SUM ( aggColumnalias1 ) OVER( PARTITION BY Deptno ) ,0 ) RATIO
     FROM
          (
               SELECT
                         SUM (salary) AS ColumnAlias1
                         ,COUNT( Salary ) aggColumnalias1
                         ,NULL AS Deptno
                         ,NULL AS Empno
                         ,Ename
                    FROM
                         emp1
                    GROUP BY
                         Ename
               UNION
               ALL SELECT
                         SUM (salary) AS ColumnAlias1
                         ,COUNT( Salary ) aggColumnalias1
                         ,Deptno
                         ,NULL AS Empno
                         ,NULL AS Ename
                    FROM
                         emp1
                    GROUP BY
                         Deptno
               UNION
               ALL SELECT
                         SUM (salary) AS ColumnAlias1
                         ,COUNT( Salary ) aggColumnalias1
                         ,NULL AS Deptno
                         ,Empno
                         ,NULL AS Ename
                    FROM
                         emp1
                    GROUP BY
                         Empno
          )
     ORDER BY
          Ename
          ,Deptno
          ,Empno
;
Parent topic: System Functions