Limit result depending on sum of value - sql

Question

I´ve been trying to automize a list of addresses in SQL. I have multiple addresses and quantities and i need only the addresses that will fulfill the quantity i need
For example:
I have a table with
Item A qty 20
Item B qty 5
Item C qty 23
And a table with addresses and units
Address 1 item A 15units
Address 2 item A 10units
Address 3 item A 10units
Address 4 item A 13units
The result should show only
Address 2 item A 10units
Address 3 item A 10units

Answer 1

Assuming that your first table sales stores the sales made :
Item
qty
A
20
B
5
C
23
and your second table stocks indicates the addresses of the stored items :
Address
item
units
1
A
15
2
A
10
3
A
10
4
A
13
then you can select a subset of addresses so that the sum of the stored units is equal or greater than the quantity sold :
WITH list AS (
SELECT st.item
, sa.qty AS sales_qty
, array_agg(st.address) OVER w AS addresses
, array_agg(st.units) OVER w AS units
, sum(units) OVER w AS total_stored_units
FROM sales AS sa
INNER JOIN stocks AS st
ON st.item = sa.item
WINDOW w AS (PARTITION BY st.item ORDER BY st.address)
)
SELECT DISTINCT ON (item)
item, unnest(addresses) AS address, unnest(units) AS units
FROM list
WHERE total_stored_units >= sales_qty
ORDER BY item, total_stored_units ASC
Result
item
address
units
A
1
15
A
2
10
see dbfiddle

Answer 2

Thanks a lot #Edouard!
I ended up using something like
WITH r AS
(
SELECT
item,
address,
quantity,
sum(quantity)
OVER (
PARTITION BY item
ORDER BY quantity desc
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
) as total_units
FROM st
GROUP BY 1,2,3
)
SELECT *
FROM r
GROUP BY 1,2,3,4
HAVING total_units <= qty_needed + avg(units)
ORDER BY units desc
I couldnt run your query in the bigquery console, but from it a re read some documentation of windows functions find this solution.
Again, thanks a lot!