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Re: Extracting data from jsonb array? - Mailing list pgsql-general

From	Ken Tanzer
Subject	Re: Extracting data from jsonb array?
Date	December 8, 2020 06:57:06
Msg-id	CAD3a31Vr_xZXnayJTu_iRvEUHRy4_P3jDqptDimFgp_xWQQMyA@mail.gmail.com Whole thread Raw
In response to	Re: Extracting data from jsonb array? (Ken Tanzer <ken.tanzer@gmail.com>)
Responses	Re: Extracting data from jsonb array? Re: Extracting data from jsonb array?
List	pgsql-general

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On Mon, Dec 7, 2020 at 7:33 PM Ken Tanzer <ken.tanzer@gmail.com> wrote:

But this has a big advantage in that you can just add other fields to the query, thusly:

=> select f.id, f.f1,f.f2,array_agg(t.key2) from foo as f, jsonb_to_recordset(js) as t(key2 text) group by f.id;
id | f1 | f2 | array_agg
----+-----------+------------+--------------------
2 | My Text 2 | My Text 2a | {r2k2val,r2k2val2}
1 | My Text 1 | My Text 1a | {r1k2val,r1k2val2}
(2 rows)

After a little more thought and experimenting, I'm not so sure about this part. In particular, I'm not clear why Postgres isn't complaining about the f1 and f2 fields. (It's not giving the "must appear in the GROUP BY clause or be used in an aggregate function" error that I would expect, and that I am getting when I try to apply this to my real query.)

Can anyone explain to me why those fields don't need to be grouped? Thanks.

Ken

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