create table t ("date" date, "value" int);
insert into t ("date", "value") values
('2011-10-31', 2),
('2011-11-01', 8),
('2011-11-02', 10),
('2012-09-13', 1),
('2012-09-14', 4),
('2012-09-15', 5),
('2012-09-16', 20),
('2012-10-30', 10);
По-проста и по-евтина версия:
select min("date"), max("date"), sum(value)
from (
select
"date", value,
"date" - (dense_rank() over(order by "date"))::int g
from t
) s
group by s.g
order by 1
Първият ми опит беше по-сложен и скъп:
create temporary sequence s;
select min("date"), max("date"), sum(value)
from (
select
"date", value, d,
case
when lag("date", 1, null) over(order by s.d) is null and "date" is not null
then nextval('s')
when lag("date", 1, null) over(order by s.d) is not null and "date" is not null
then lastval()
else 0
end g
from
t
right join
generate_series(
(select min("date") from t)::date,
(select max("date") from t)::date + 1,
'1 day'
) s(d) on s.d::date = t."date"
) q
where g != 0
group by g
order by 1
;
drop sequence s;
Резултатът:
min | max | sum
------------+------------+-----
2011-10-31 | 2011-11-02 | 20
2012-09-13 | 2012-09-16 | 30
2012-10-30 | 2012-10-30 | 10
(3 rows)