Hi Franz,
It looks like you are trying to solve a comulative sum. You don’t need the lag function, instead you should use sum and you will get a desired result:
Select ts, c, sum(c) over(order by ts) c2 from tt order by ts;
Best,
Igor
Hi Franz,
Simply you can use window functions[1][2].
pgsql-sql=# select *, lag(c) over (order by ts) as c2 from tt;
ts | c | c2
---------------------+---+----
2019-12-31 00:00:00 | 1 |
2020-01-01 00:00:00 | 2 | 1
2020-07-02 00:00:00 | 3 | 2
2020-07-06 00:00:00 | 4 | 3
2020-07-07 00:00:00 | 5 | 4
2020-07-08 00:00:00 | 6 | 5
(6 rows)
I personally prefer to use window functions due to their simplicity. If you still want to use recursive query: [3]
pgsql-sql=# with recursive rc as (
select * from (select ts,c,null::numeric as c2 from tt order by ts asc limit 1) k1
union
select * from (select tt.ts,tt.c,rc.c as c2 from tt, lateral (select * from rc) rc where tt.ts > rc.ts order by tt.ts asc limit 1) k2
)
select * from rc;
ts | c | c2
---------------------+---+----
2019-12-31 00:00:00 | 1 |
2020-01-01 00:00:00 | 2 | 1
2020-07-02 00:00:00 | 3 | 2
2020-07-06 00:00:00 | 4 | 3
2020-07-07 00:00:00 | 5 | 4
2020-07-08 00:00:00 | 6 | 5
(6 rows)
Best regards.
Samed YILDIRIM
Hello,
the table
create table tt (
ts timestamp,
c numeric) ;
insert into tt values
('2019-12-31',1), ('2020-01-01',2),
('2020-07-02',3), ('2020-07-06',4),
('2020-07-07',5), ('2020-07-08',6);
My question: It is possible to get an
additional column (named c2)
with
( c from current row ) + ( c2 from the previous row ) as c2
the result:
ts c c2
.. 1 1 -- or null in the first row
.. 2 3
.. 3 6
.. 4 10
...
with recursive ema as ()
select ts, c,
-- many many computed_rows
-- <code> as c2
from tt -- <- I need tt on this place
thank you for help
Franz
