Thanks!
I'll investigate (explain) performance for both versions.
Edson Richter
------ Mensagem original ------
De: David Johnston
Data: 04/07/2014 21h20
Para: Edson Richter;
Cc:pgsql-general@xxxxxxxxxxxxxx;
Assunto:Re: Re : [GENERAL] Query "top 10 and others"
> with QRY as (select C1.country, C1.state, sum(C1.population) > from places C1 > group by 1, 2 > order by 3 DESC > limit 10) > > select * from QRY > union > select 'others' as "country", '' as "state", sum(population) > from places > where not exists (select 1 from QRY where country = QRY.country and state > = QRY.state) >
(not tested)
with QRY as ( SELECT country, state, sum(population) as st_pop FROM places GROUP BY country, state )
, u1 AS ( SELECT country, state, st_pop FROM QRY ORDER BY st_pop DESC LIMIT 10 )
, u2 AS ( SELECT 'other' AS country, '' AS state, sum(st_pop) FROM QRY WHERE NOT EXISTS (
SELECT 1 FROM u1 WHERE (QRY.country, QRY.state) = (u1.country, u1,state)
)
SELECT * FROM u1
UNION ALL
SELECT * FROM u2
;
David J.
