[jira] [Created] (CALCITE-704) FILTER clause for aggregate functions

["Julian Hyde (JIRA)" <ji...@apache.org>]

Julian Hyde created CALCITE-704:
-----------------------------------

             Summary: FILTER clause for aggregate functions
                 Key: CALCITE-704
                 URL: https://issues.apache.org/jira/browse/CALCITE-704
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde
            Assignee: Julian Hyde


The SQL standard provides a means to control which values are accumulated by an aggregate function.

{code}aggregate function> ::=
    COUNT <left paren> <asterisk> <right paren> [ <filter clause> ]
  | <general set function> [ <filter clause> ]
  | <binary set function> [ <filter clause> ]
  | <ordered set function> [ <filter clause> ]
  | <array aggregate function> [ <filter clause> ]

<filter clause> ::=
  FILTER <left paren> WHERE <search condition> <right paren>{code}

For example, the following query sums the salary of all employees and female employees in a particular department:

{code}SELECT deptno,
  SUM(sal) AS all_sal,
  SUM(sal) FILTER ( WHERE gender = 'F' ) AS female_sal
FROM emp
GROUP BY deptno{code}

You could previously achieve this using {{SUM(CASE WHEN gender = 'F' THEN sal ELSE null END)}} but that trick only worked on certain aggregate functions.



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