Re: Group by column alias where same-column-name already exists - Mailing list pgsql-sql

Nice solution!

Thank you so mutch!

Il 11/12/18 17:51, Voillequin, Jean-Marc ha scritto:
> "...group by 1, first_table.c2"
>
> should do the trick.
>
> -----Original Message-----
> From: agharta82@gmail.com [mailto:agharta82@gmail.com]
> Sent: Tuesday, December 11, 2018 5:40 PM
> To: pgsql-sql@lists.postgresql.org
> Subject: Group by column alias where same-column-name already exists
>
>
>
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>
> Hi all,
>
> A little question about grouping by a computed column alias where other columns with same name exists.
>
> Take look at this query (don't take care about, it was created as a test to explain my question).
>
> select case when (second_table.c1 = 'X') then '1' else '2' end as c1,
> first_table.c2
> from (
>       select 'A'::text as c1, 'B'::text as c2
> ) first_table
> inner join (
>       select 'X'::text as c1
>       union
>       select 'W'::text as c1
>       union
>       select 'X'::text as c1
> )  second_table on (true)
> group by c1, first_table.c2
>
>
> I have a computed coulmn alias in select called c1 (select case when
> (second_table.c1 = 'X') then '1' else '2' end as c1)
>
> I want to group by that alias c1 (group by c1)
>
> BUT first_table has a c1 column and second_table has a c1 column too!
>
> If i run the query it returns "ERROR: column reference "c1" is ambiguous"
>
> Someone knows a way to solve this?
>
> Not replacing grou by alias with its case and without changing column names, oblivious.
>
> In other dbs (like firebird) main (computed ) select column alias name takes precedence in group by clause. So if i
groupby c1 that means the computed (case when.... ) c1 in that case. 
>
>
> Best regards,
>
> Agharta
>
>
>
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