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https://issues.apache.org/jira/browse/DERBY-5466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14639540#comment-14639540
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Scott Lewis commented on DERBY-5466:
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Thanks Rick for the explanation.
Hmmm. Although I think it would ultimately be much more convenient for users
to have these as built-in Derby aggregates, I'm not sure if I can commit the
time necessary to do '2'. I've looked at the source for (e.g.) AvgAggregator
(which extends SumAggregator extends OrderableAggregator extends
SystemAggregator), and it looks quite different from the Aggregator API.
Would it be possible to get some committer collaboration (and/or documentation)
for '2'? I think it would be better to do 2 from user perspective for these
four functions (since they are apparently supported natively on so many other
SQL impls), but I don't think I can commit to doing everything that appears to
be required for '2'.
> Add support for SQL Standard statistics functions, such as STDDEV_POP,
> STDDEV_SAMP, VAR_POP, VAR_SAMP
> -----------------------------------------------------------------------------------------------------
>
> Key: DERBY-5466
> URL: https://issues.apache.org/jira/browse/DERBY-5466
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.8.1.2
> Reporter: Lukas Eder
> Priority: Minor
> Labels: derby_triage10_10
>
> Any of these RDBMS support the SQL standard statistics functions STDDEV_POP,
> STDDEV_SAMP, VAR_POP, VAR_SAMP:
> - DB2 (only STDDEV, VARIANE)
> - H2
> - HSQLDB
> - Ingres
> - MySQL
> - Oracle
> - Postgres
> - SQL Server (named STDEVP, STDEV, VARP, VAR)
> - Sybase ASE
> - Sybase SQL Anywhere
> These don't:
> - Derby
> - SQLite
> This would be a useful addition for Derby, I think.
> An even larger example list of possible statistics aggregate functions is
> listed in the Postgres documentation:
> http://www.postgresql.org/docs/9.0/static/functions-aggregate.html#FUNCTIONS-AGGREGATE-STATISTICS-TABLE
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