Sql update table with joined sums of other tables - sql

Question

I'm trying to reduce storage with packages included in sold products.
Products can have different amounts of same packages and invoice can have different amounts of products in separate lines. Action should be performed against certain invoiceID.
Simplified tables (summary is not column, just added to ease up calculation):
Inv_rows
InvID ProdID Qty *Summary*
999 100 2 *100 = 10*
999 101 2 *101 = 2*
999 102 2 *102 = 2*
999 103 2 *103 = 10*
999 100 8
999 103 8
Pack_to_prod
ProdID PackID Qty
100 A 2 *A = 20*
100 B 1 *B = 10*
101 A 1 *A = 2*
101 B 1 *B = 2*
102 A 3 *A = 6*
103 B 2 *B = 20*
Storage
ItemID Qty
A 100 *A = 28*
B 100 *B = 32*
**Desired Result**
Storage
ItemID Qty
A 72 *(100-28)*
B 68 *(100-32)*
What I have tried is:
UPDATE Storage
SET Storage.Qty = Storage.Qty -
(SELECT SUM (Inv_rows.Qty * Pack_to_prod.Qty) FROM Inv_rows
WHERE Inv_rows.ProdID IN (SELECT ProdID FROM Pack_to_prod
WHERE Pack_to_prod.PackID=Storage.ItemID) AND Inv_rows.InvId = 999
)
FROM Inv_rows, Storage, Pack_to_prod
WHERE Inv_rows.ProdID = Pack_to_prod.ProdID
AND Pack_to_prod.PackID = Storage.ItemID
AND Inv_rows.InvID = 999
But the problem is the 'IN' since it doesn't match the rows but I can't use '=' as 'where' results more than one line.
Then I tried to simplify it for myself (as I'm not a professional) with a select clause to understand what exactly needs to be done..
SELECT
Pack_to_prod.PackID AS PackageID,
Inv_rows.ProdID AS ProductID,
Inv_rows.Qty AS ProductQty,
Pack_to_prod.Qty AS PackageQtyPerProduct,
Inv_rows.Qty*Pack_to_prod.Qty AS PackageTotal,
Storage.Qty AS StorageQty,
Storage.Qty - (Inv_rows.Qty * Pack_to_prod.Qty) AS NewStorageQty
FROM Pack_to_prod,Inv_rows,Storage
WHERE Inv_rows.ProdID = Pack_to_prod.ProdID
AND Pack_to_prod.PackID = Storage.ItemID
AND Inv_rows.InvID = 999
GROUP BY Inv_rows.ProdID, Pack_to_prod.PackID, Pack_to_prod.Qty, Storage.Qty, Inv_rows.Qty
Which results as simple list showing the problem why they can't be just summed up:
PackageID ProductID ProductQty PackageQtyPerProduct PackageTotal StorageQty NewStorageQty
A 100 2 2 4 100 96
A 100 8 2 16 100 84
B 100 2 1 2 100 98
B 100 8 1 8 100 92
A 101 2 1 2 100 98
B 101 2 1 2 100 98
A 102 2 3 6 100 94
B 103 2 2 4 100 96
B 103 8 2 16 100 84
But can't figure out how to make it run 'line by line' so that each 'Pack_to_prod.Qty' would be handled separately.
Any help in right direction appreciated.

Answer 1

This seems like some aggregations and joins. To get the changes in values, then:
select pp.packid, sum(p.qty * pp.qty) as new_qty
from (select ir.prodid, sum(qty) as qty
from inv_rows ir
group by ir.prodid
) p join
Pack_to_prod pp
on pp.prodid = p.prodid
group by pp.packid;
You can then use this in an update:
update s
set s.qty = s.qty - pp.new_qty
from storage s join
(select pp.packid, sum(p.qty * pp.qty) as new_qty
from (select ir.prodid, sum(qty) as qty
from inv_rows ir
group by ir.prodid
) p join
Pack_to_prod pp
on pp.prodid = p.prodid
group by pp.packid
) pp
on pp.packid = s.itemid;

Answer 2

This was explained very well. The SQL code is user older coding conventions (such as JOIN conditions in the WHERE clause, instead of FROM) and isn't organized into subqueries properly. All the pieces are present though. I think something like this is what you're looking for.
with
inv_cte(ProdID, sum_qty) as (
select ProdID, sum(Qty)
from Inv_rows
group by ProdID),
pack_cte(PackID, prod_qty) as (
select pp.PackID, sum(pp.Qty*ic.sum_qty)
from Pack_to_prod pp
join inv_cte ic on pp.ProdID=ic.ProdID
group by pp.PackID)
select s.ItemID, s.Qty-p.prod_qty as ResultQty
from Storage s
join pack_cte p on s.ItemID=p.PackID;
Update statement
with
inv_cte(ProdID, sum_qty) as (
select ProdID, sum(Qty)
from Inv_rows
group by ProdID),
pack_cte(PackID, prod_qty) as (
select pp.PackID, sum(pp.Qty*ic.sum_qty)
from Pack_to_prod pp
join inv_cte ic on pp.ProdID=ic.ProdID
group by pp.PackID)
update s
set Qty=Qty-p.prod_qty
from Storage s
join pack_cte p on s.ItemID=p.PackID;