aggregates, distinct, order by, and case - why won't this work - Mailing list pgsql-general

From David G. Johnston
Subject aggregates, distinct, order by, and case - why won't this work
Date
Msg-id CAKFQuwb0VYBFk_Fnjbi4tbYRVsAXWD1xNOnzF=N=h=CR0z9DGg@mail.gmail.com
Whole thread Raw
Responses Re: aggregates, distinct, order by, and case - why won't this work  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
This...on 9.3

SELECT array_agg(
distinct case when v % 2 = 0 then 'odd' else 'even' end 
order by case when v % 2 = 0 then 1 else 2 end
)
FROM (VALUES (1), (2), (3)) val (v)

I'm not particularly irked at this though I was hoping to fix a somewhat complex query of mine by simply adding a "DISTINCT" to the array_agg that I am building from derived (using CASE) data.

I am curious to the reason for the limitation, particularly as it would relate to this specific instance.

Any givers?

Thank!

David J.

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