Cumulative Sum over 12 months by Postgreql 10

Question

I am new to window functioning in postgresql. I have 10 columns in my data set and i want to do the running total based on the MM-YYYY but keep fail to get the correct amount. I tried to manual download the data and sum and there have no problem.

Sample Data as below

+--------------+--------+--------------+---------+-----------+--------------+-------------+------------+--------------+-------------+
| document_no  |  type  |  year_month  |  accty  |  account  |  gl_account  |  doc_date   |    amt     |  pstng_date  |  entry_date |
+--------------+--------+--------------+---------+-----------+--------------+-------------+------------+--------------+-------------+
|   100014096  |  AB    |  2019/01     |  D      |  A        |      123456  |  12/1/2019  |  75008     |  12/1/2019   |  12/1/2019  |
|   100014096  |  AB    |  2019/02     |  D      |  A        |      123457  |  12/2/2019  |  5008      |  12/2/2019   |  12/2/2019  |
|   100014098  |  AB    |  2019/03     |  D      |  B        |      123458  |  12/3/2019  |  93745     |  12/3/2019   |  12/3/2019  |
|   100014098  |  AB    |  2019/04     |  D      |  B        |      123459  |  12/4/2019  |  3745      |  12/4/2019   |  12/4/2019  |
|   100014106  |  AB    |  2019/05     |  D      |  C        |      123460  |  1/5/2019   |  2434047   |  1/5/2019    |  1/5/2019   |
|   100014106  |  AB    |  2019/06     |  D      |  C        |      123461  |  1/6/2019   |  434047    |  1/6/2019    |  1/6/2019   |
|   100015139  |  AB    |  2019/06     |  D      |  C        |      123462  |  1/6/2019   |  11000     |  1/6/2019    |  1/6/2019   |
|   100015987  |  AB    |  2019/06     |  D      |  D        |      123463  |  1/6/2019   | -22124.85  |  1/6/2019    |  1/6/2019   |
+--------------+--------+--------------+---------+-----------+--------------+-------------+------------+--------------+-------------+

When i tried to use window function to sum it and partition over account and order by date then i cant get the right answer.

Example:

Feb-19 running_total should be (75008 + 5008 = 80016)‬  
Mar-19 running_total should be (75008 + 5008 + 93745 = 173761)‬
Apr-19 running_total should be (75008 + 5008 + 93745 + 3745 = 177506)‬

Below is my sql code, any hints? I have tried those solution found at forum but still to fail get the answer

WITH temp AS(
SELECT 
    (year_month || '/01')::date AS file_date,
    SUM(amt) AS amt,
    sum(amt) OVER (PARTITION BY account ORDER BY (year_month || '/01')::date
                    ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS rollover
   FROM table.sample_data
    WHERE type <> 'DZ' AND ((year_month || '/01')::date >= (date_trunc('month', current_date) - interval '1 year'))
    GROUP BY amt, type, account, year_month
    ORDER BY year_month DESC
)
SELECT file_date,
    SUM(amt) AS amt,
    SUM(rollover) AS rollover
    FROM temp 
        GROUP BY file_date
        ORDER BY file_date DESC

Answer 1

Will this be enough for you?

SELECT
  b.file_date,
  SUM(a.amt) AS amt,
  SUM(SUM(a.amt)) OVER(ORDER BY b.file_date
                       ROWS UNBOUNDED PRECEDING) AS rollover
FROM sample_data AS a
INNER JOIN LATERAL (SELECT TO_DATE(a.year_month, 'yyyy/mm') AS file_date) AS b
  ON TRUE
WHERE
  a."type" <> 'DZ' AND
  b.file_date >= DATE_TRUNC('MONTH', CURRENT_DATE) - INTERVAL '1 YEAR 6 MONTHS'
GROUP BY b.file_date;

Results:

+------------+------------+------------+
| file_date  |    amt     |  rollover  |
+------------+------------+------------+
| 2019-01-01 | 75008.00   | 75008.00   |
| 2019-02-01 | 5008.00    | 80016.00   |
| 2019-03-01 | 93745.00   | 173761.00  |
| 2019-04-01 | 3745.00    | 177506.00  |
| 2019-05-01 | 2434047.00 | 2611553.00 |
| 2019-06-01 | 422922.15  | 3034475.15 |
+------------+------------+------------+

Demo.