Perché raggruppamento in una sottoquery causa problemi

Question

Quando includo le 2 linee commentato nel seguente subquery, sembra che ci vuole per sempre fino a quando il mio Sybase ASE 12.5 assistente ottiene alcun risultato. Senza queste 2 righe la query viene eseguita ok. Cosa c'è di così sbagliato in questo raggruppamento?

select days_played.day_played, count(distinct days_played.user_id) as OLD_users
from days_played inner join days_received
on days_played.day_played = days_received.day_received
and days_played.user_id = days_received.user_id
where days_received.min_bulk_MT > days_played.min_MO
and days_played.user_id in

(select sgia.user_id 
from days_played as sgia
where sgia.day_played < days_played.day_played
--group by sgia.user_id 
--having sum(sgia.B_first_msg) = 0
)

group by days_played.day_played

Answer 1

ok ho scoperto quale fosse il problema Ho dovuto includere id utente nel subquery: "dove days_played.user_id = sgia.user_id e sgia.day_played

Answer 2

Scopri che la query fa utilizzando showplan per mostrare la spiegazione.

In questo caso non puoi eliminare la sottoquery rendendolo parte della query principale?

Answer 3

Potresti provare a riscrivere la query come segue?

select days_played.day_played,
       count(distinct days_played.user_id) as OLD_users
  from days_played
 inner join days_received on days_played.day_played = days_received.day_received
                         and days_played.user_id = days_received.user_id
 where days_received.min_bulk_MT > days_played.min_MO
   and 0 = (select sum(sgia.B_first_msg)
              from days_played as sgia
             where sgia.user_id = days_played.user_id
               and sgia.day_played < days_played.day_played
            )
 group by days_played.day_played

Credo che questo dovrebbe dare prestazioni migliori ...