MySQL Bugs: #119502: Implement distinct count/sum window functions

Bug #119502	Implement distinct count/sum window functions
Submitted:	3 Dec 2025 15:54	Modified:	8 Dec 2025 21:36
Reporter:	Yoni Sade	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: Optimizer	Severity:	S4 (Feature request)
Version:	9.5	OS:	Any
Assigned to:		CPU Architecture:	Any

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Description:
Other databases already implemented the option for aggregating only distinct values:

COUNT(DISTINCT [value column]) OVER (PARTITION BY [partition column])

SUM(DISTINCT [value column]) OVER (PARTITION BY [partition column])

How to repeat:
SELECT COUNT(DISTINCT id) OVER (PARTITION BY id) FROM (SELECT 1 id) x

Gives error:

SQL Error [1235] [42000]: This version of MySQL doesn't yet support '<window function>(DISTINCT ..)'

Thank you for the reasonable feature request.