Re: STRING_AGG and GROUP BY

Hi David -

On Fri, Mar 16, 2018 at 4:40 PM, David G. Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com> wrote:

> ​First reaction is to ARRAY_AGG(DISTINCT x) and then write a function that
> converts ​that array into a string by extracting 'letter' from each cell in
> the array.
>
> Thinking it over a bit you have two columns that both are aggregates but
> that are otherwise independent of each other. Since they are independent
> they cannot be aggregated at the same time. You need to write a two
> subqueries, either in the target list or as separate from/join items, and
> then join the already aggregated queries together on their common group by
> column.
>
> The presence of DISTINCT here (and, IMO, generally), even if it worked,
> would be an indicator that something is not quite right.
>
>
thank you for confirming my feeling that DISTINCT is a bad indicator here...

But you say that "tiles" and "word (score)" are unrelated and this does
not seem true to me:

For each move id aka "mid" there is a JSON value, describing how the player
played the letter tiles.
And for the same "mid" there is a list of one or more "word (score)"s
achieved...

Maybe it is possible to GROUP BY tiles somehow or some kind of special SQL
JOIN?

Regards
Alex