Re: PostgreSQL query with FULL OUTER JOIN and subquery using column of GROUP BY expression ERROR: subquery uses ungrouped column from outer query

On 2/25/26 3:14 AM, PALAYRET Jacques wrote:
> Hello,
>
> I have 3 tables : t1, t2 and t3
> t1(posx integer, posy integer, dat timestamp, val_grid numeric)
>   with Primary Key=(posx, posy, dat)
> t2(id integer, x integer, y integer)
>   with Primary Key=(id)
> t3(id integer, dat timestamp, c1 numeric)
>   with Primary Key=(id, dat)
>
> My (very simplified) query  that doesn't work:
> SELECT
>   id, to_char(dat, 'YYYYMM'), CASE
> FLOOR((TO_NUMBER(TO_CHAR(dat,'DD'),'99')-1)/10) WHEN 0 THEN 1 WHEN 1
> THEN 2 ELSE 3 END::smallint,
> avg(val_grid), sum(c1),
> *(SELECT col1 FROM another_table WHERE another_table.np=id LIMIT 1)*
> FROM
>   (SELECT * FROM t1 ) AS t1
> *JOIN* t2  ON (t1.posx=t2.x AND t1.posy=t2.y)
> *FULL OUTER JOIN* (SELECT * FROM t3   ) t3 USING(id, dat)
> --WHERE ...
> *GROUP BY* id, to_char(dat, 'YYYYMM'), CASE
> FLOOR((TO_NUMBER(TO_CHAR(dat,'DD'),'99')-1)/10) WHEN 0 THEN 1 WHEN 1
> THEN 2 ELSE 3 END::smallint
> ;
> ERROR:  subquery uses ungrouped column "t2.id" from outer query
>
> -> The problem is on the third line (the subquery) :
> (SELECT col1 FROM another_table WHERE another_table.np=id LIMIT 1)
>
> However, If I replace "FULL OUTER" by "*LEFT OUTER*" or by "*RIGHT
> OUTER*", *it works*.
>
> Could you please tell me how to correct the query, to fix this problem?

Questions:

1) Why FROM (SELECT * FROM t1 ) AS t1 instead of just FROM t1?
Same for JOIN (SELECT * FROM t3 ) t3

2) Why are the field names not table qualified e.g. t2.id, t3.id, etc?

3) What is the desired outcome?

>
> Regards
> ----- Météo-France -----
> PALAYRET Jacques
> DCSC/GDC
> jacques(dot)palayret(at)meteo(dot)fr
> Fixe : +33 561078319

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com