PostgreSQL，一次有两个窗口函数

Question

我有典型的 table 数据，比如 mytemptable。

DROP TABLE IF EXISTS mytemptable; 
CREATE TEMP TABLE mytemptable 
       (mydate date, somedoc text, inqty int, outqty int); 
INSERT INTO mytemptable (mydate, somedoc, inqty, outqty) 
VALUES ('01.01.2016.', '123-13-24', 3, 0), 
       ('04.01.2016.', '15-19-44',  2, 0), 
       ('06.02.2016.', '15-25-21',  0, 1), 
       ('04.01.2016.', '21-133-12', 0, 1), 
       ('04.01.2016.', '215-11-51', 0, 2), 
       ('05.01.2016.', '11-181-01', 0, 1), 
       ('05.02.2016.', '151-80-8',  4, 0), 
       ('04.01.2016.', '215-11-51', 0, 2), 
       ('07.02.2016.', '34-02-02',  0, 2); 

SELECT row_number() OVER(ORDER BY mydate) AS rn, 
       mydate, somedoc, inqty, outqty, 
       SUM(inqty-outqty) OVER(ORDER BY mydate) AS csum 
  FROM mytemptable 
 ORDER BY mydate;

在我的 SELECT 查询中，我尝试按日期对结果进行排序并添加行号 'rn' 和累积（传递）总和 'csum'。当然没有成功。
我相信这是因为我在查询中使用了两个以某种方式发生冲突的窗口函数。

如何正确地使此查询快速、有序并在 'csum' 列 (3, 5, 4, 2, 0, -1, 3, 2, 0) 中获得正确的结果

Answer 1

由于在 2016-04-01 处存在排序关系，因此这些行的结果将是总和。如果您希望它有所不同，请使用 order by.

中的解开列

From the manual:

There is another important concept associated with window functions: for each row, there is a set of rows within its partition called its window frame. Many (but not all) window functions act only on the rows of the window frame, rather than of the whole partition. By default, if ORDER BY is supplied then the frame consists of all rows from the start of the partition up through the current row, plus any following rows that are equal to the current row according to the ORDER BY clause. When ORDER BY is omitted the default frame consists of all rows in the partition

如果没有解开列，您可以在外部查询中使用生成的行号：

set datestyle = 'dmy';
with mytemptable (mydate, somedoc, inqty, outqty) as (
    values
    ('01-01-2016'::date, '123-13-24', 3, 0), 
    ('04-01-2016', '15-19-44',  2, 0), 
    ('06-02-2016', '15-25-21',  0, 1), 
    ('04-01-2016', '21-133-12', 0, 1), 
    ('04-01-2016', '215-11-51', 0, 2), 
    ('05-01-2016', '11-181-01', 0, 1), 
    ('05-02-2016', '151-80-8',  4, 0), 
    ('04-01-2016', '215-11-51', 0, 2), 
    ('07-02-2016', '34-02-02',  0, 2)
)
select *, sum(inqty-outqty) over(order by mydate, rn) as csum
from (
    select
        row_number() over(order by mydate) as rn, 
        mydate, somedoc, inqty, outqty
    from mytemptable
) s
order by mydate;
 rn |   mydate   |  somedoc  | inqty | outqty | csum 
----+------------+-----------+-------+--------+------
  1 | 2016-01-01 | 123-13-24 |     3 |      0 |    3
  2 | 2016-04-01 | 15-19-44  |     2 |      0 |    5
  3 | 2016-04-01 | 21-133-12 |     0 |      1 |    4
  4 | 2016-04-01 | 215-11-51 |     0 |      2 |    2
  5 | 2016-04-01 | 215-11-51 |     0 |      2 |    0
  6 | 2016-05-01 | 11-181-01 |     0 |      1 |   -1
  7 | 2016-05-02 | 151-80-8  |     4 |      0 |    3
  8 | 2016-06-02 | 15-25-21  |     0 |      1 |    2
  9 | 2016-07-02 | 34-02-02  |     0 |      2 |    0

PostgreSQL，一次有两个窗口函数

PostgreSQL, two windowing functions at once

postgresql

window-functions