[
http://issues.apache.org/jira/browse/DERBY-672?page=comments#action_12457874 ]
Rick Hillegas commented on DERBY-672:
-------------------------------------
I do not see ANSI syntax for this feature. Here is the syntax used by some
other databases.
----------------------------------------
Cloudscape 3.5:
CREATE AGGREGATE AggregateName FOR
{ JavaClassName | ClassAlias }
The aliased class has to be an implementation of a Cloudscape interface
(COM.cloudscape.aggregates.AggregateDefinition). That, in turn, means that the
class has to implement a couple methods:
accumulate() -- accumulator for non-grouped results
getResult() -- the final result of the accumulation
merge() -- accumulator for grouped results
---------------------------------------
Postgres 8.0.0:
CREATE AGGREGATE name (
BASETYPE = input_data_type,
SFUNC = sfunc,
STYPE = state_data_type
[ , FINALFUNC = ffunc ]
[ , INITCOND = initial_condition ]
)
Here
SFUNC is the name of an accumulator function
FFUNC is the name of a function which returns the accumulated result
-----------------------------------------------------------
IBM Informix:
CREATE AGGREGATE average
WITH (
INIT = initFunction,
ITER = iterationFunction,
COMBINE = combinationFunction,
FINAL = resultFunction
)
where
initFunction is a function initializing the accumulator
iterationFunction a counting function
combinationFunction an accumulator function
resultFunction a function which returns the accumulated result
> Re-enable user defined aggregates
> ---------------------------------
>
> Key: DERBY-672
> URL: http://issues.apache.org/jira/browse/DERBY-672
> Project: Derby
> Issue Type: New Feature
> Components: SQL
> Reporter: Rick Hillegas
>
> Nicolas Dufour in an email thread titled "functions and list" started on
> November 2, 2005 requests the ability to create user defined aggregates.
> This functionality used to be in Cloudscape. It was disabled presumably
> because it was considered non-standard. However, most of the machinery needed
> for this feature is still in the code. We should re-enable user defined
> aggregates after we agree on acceptable syntax.
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