Hello
I am play with windows function. I was surprised so these queries has
different results.
postgres=# select sum(a) over (partition by b), a, b from foo;sum | a | b
-----+----+--- 19 | 1 | 1 19 | 1 | 1 19 | 2 | 1 19 | 4 | 1 19 | 2 | 1 19 | 4 | 1 19 | 5 | 1 93 | 11 | 3 93 | 12
|3 93 | 22 | 3 93 | 16 | 3 93 | 16 | 3 93 | 16 | 3
(13 rows)
postgres=# select sum(a) over (partition by b order by a), a, b from foo;sum | a | b
-----+----+--- 2 | 1 | 1 2 | 1 | 1 6 | 2 | 1 6 | 2 | 1 14 | 4 | 1 14 | 4 | 1 19 | 5 | 1 11 | 11 | 3 23 | 12
|3 71 | 16 | 3 71 | 16 | 3 71 | 16 | 3 93 | 22 | 3
(13 rows)
I didn't expect so ORDER can change result of function sum. Please,
can somebody explain it?
regards
Pavel Stehule
