remove outliers by group in sql - sql

Question

In my column in SQL Server, I must delete outliers for each group separately. Here are my columns
select
customer,
sku,
stuff,
action,
acnumber,
year
from
mytable
Sample data:
customer sku year stuff action
-----------------------------------
1 1 2 2017 10 0
2 1 2 2017 20 1
3 1 3 2017 30 0
4 1 3 2017 40 1
5 2 4 2017 50 0
6 2 4 2017 60 1
7 2 5 2017 70 0
8 2 5 2017 80 1
9 1 2 2018 10 0
10 1 2 2018 20 1
11 1 3 2018 30 0
12 1 3 2018 40 1
13 2 4 2018 50 0
14 2 4 2018 60 1
15 2 5 2018 70 0
16 2 5 2018 80 1
I must delete outlier from stuff variable, but separately by group customer+sku+year.
All that is below the 25th percentile and above 75 percentile should be considered an outlier and this principle must be respected for each group.
How to clear dataset for next working ?
Note, in this dataset, there is variable action (it tales value 0 and 1). It is not group variable, but outliers must be delete only for ZERO(0) categories of action variable.
in R language this is decided as
remove_outliers <- function(x, na.rm = TRUE, ...) {
qnt <- quantile(x, probs=c(.25, .75), na.rm = na.rm, ...)
H <- 1.5 * IQR(x, na.rm = na.rm)
y <- x
y[x < (qnt[1] - H)] <- NA
y[x > (qnt[2] + H)] <- NA
y
}
new <- remove_outliers(vpg$stuff)
vpg=cbind(new,vpg)

Answer 1

Something like this, maybe:
DELETE mytable
WHERE PERCENT_RANK() OVER (PARTITION BY Department ORDER BY customer, sku, year ORDER BY stuff ) < .25 OR
PERCENT_RANK() OVER (PARTITION BY Department ORDER BY customer, sku, year ORDER BY stuff ) > .75