Create or add random number to fulfill some condition - google-bigquery

Question

I have data like this..
month_date location sales
2022-01-01 Asia 150
2022-01-01 Europe 250
2022-02-01 Asia 100
2022-02-01 Europe 100
and breakdown by day_date
day_date location sales
2022-01-01 Asia 12
2022-01-02 Asia 10
2022-01-03 Asia 15
2022-01-04 Asia 19
2022-01-05 Asia 15
2022-01-06 Asia 11
....
2022-01-31 Asia 2
total: Asia 132
but when I compare sales between month_date=150 and day_date=132 I still have minus 18.
is it possible to add random data which contain minus 18 but breakdown by day_date?
like below
day_date location sales
2022-01-01 Asia 13
2022-01-02 Asia 11
2022-01-03 Asia 16
2022-01-04 Asia 20
2022-01-05 Asia 16
2022-01-06 Asia 12
....
2022-01-31 Asia 2
total: Asia 150

Answer 1

You might consider below. (diff number, 18 in this case, will be added by one starting from 1st day of month.)
SELECT day_date, location,
sales + DIV(diff, days) + IF(EXTRACT(DAY FROM day_date) <= MOD(diff, days), 1, 0) AS sales
FROM (
SELECT d.*,
m.sales - SUM(d.sales) OVER w AS diff,
DATE_DIFF(LAST_DAY(month_date), month_date, DAY) AS days
FROM day_table d
LEFT JOIN month_table m
ON DATE_TRUNC(d.day_date, MONTH) = m.month_date AND d.location = m.location
WINDOW w AS (PARTITION BY DATE_TRUNC(day_date, MONTH), d.location)
);
Query results