Running Total of all Previous Rows BigQuery - sql

Question

I have a BigQuery Table which looks like Below:
ID SessionNumber CountOfAction Category
1 1 1 B
1 2 3 A
1 3 1 A
1 4 4 B
1 5 5 B
I am trying to get the running total of all previous rows for CountofAction where category = A. The final Output should be
ID SessionNumber CountOfAction
1 1 0 --no previous rows have countofAction for category = A
1 2 0 --no previous rows have countofAction for category = A
1 3 3 --previous row (Row 2) has countofAction = 3 for category = A
1 4 4 --previous rows (Row 2 and 3) have countofAction = 3 and 1 for category = A
1 5 4 --previous rows (Row 2 and 3) have countofAction = 3 and 1 for category = A
Below is the query I have written but it doesn't give me desired output
select
ID,
SessionNumber ,
SUM(CountofAction) OVER(Partition by clieIDntid ORDER BY SessionNumber ROWS BETWEEN UNBOUNDED
PRECEDING AND 1 PRECEDING)as CumulativeCountofAction
From TAble1 where category = 'A'
I would really appreciate any help on this! Thanks in advance

Answer 1

Filtering on category in the where clause evicts (id, sessionNumber) tuples where category 'A' does not appear, which is not what you want.
Instead, you can use aggregation and a conditional sum():
select
id,
sessionNumber,
sum(sum(if(category = 'A', countOfAction, 0))) over(
partition by id
order by sessionNumber
rows between unbounded preceding and 1 preceding
) CumulativeCountofAction
from mytable t
group by id, sessionNumber
order by id, sessionNumber

Answer 2

Below is for BigQuery Standard SQL
#standardSQL
SELECT ID, SessionNumber,
IFNULL(SUM(IF(category = 'A', CountOfAction, 0)) OVER(win), 0) AS CountOfAction
FROM `project.dataset.table`
WINDOW win AS (ORDER BY SessionNumber ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING)
If to apply to sample data from your question as in below example
#standardSQL
WITH `project.dataset.table` AS (
SELECT 1 ID, 1 SessionNumber, 1 CountOfAction, 'B' Category UNION ALL
SELECT 1, 2, 3, 'A' UNION ALL
SELECT 1, 3, 1, 'A' UNION ALL
SELECT 1, 4, 4, 'B' UNION ALL
SELECT 1, 5, 5, 'B'
)
SELECT ID, SessionNumber,
IFNULL(SUM(IF(category = 'A', CountOfAction, 0)) OVER(win), 0) AS CountOfAction
FROM `project.dataset.table`
WINDOW win AS (ORDER BY SessionNumber ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING)
result is
Row ID SessionNumber CountOfAction
1 1 1 0
2 1 2 0
3 1 3 3
4 1 4 4
5 1 5 4