Distribute values to several rows in SQL Server - sql

Question

I need help with SQL Server on how to distribute a row value to several rows with the same id. To illustrate,
Id = ProductInventoryCode
Qty = QuantityInStock
ForDistribution:
Id | Qty | TotalNoOfBranchesWithId
---+--------+-------------------------
1 | 40 | 2
2 | 33 | 3
3 | 21 | 2
A table that will receive the distributed values
Id | BranchCode | Qty | QtyFromForDistributionTable
-------------------------------------------------------
1 101 13 20
1 102 8 20
2 101 10 11
2 102 2 10
2 103 3 12
3 101 1 11
3 102 12 10
As much as possible the distribution should be near equal for each id and branches.
I got something like below, but somewhat got confused and lost path.
with rs as
(
select
r.*, cume.cumequantity,
coalesce(s.shipped, 0) AS shipped
from
tmpForDistribution r
cross apply
(SELECT SUM([QuantityInStock]) AS cumequantity
FROM tmpForDistribution r2
WHERE r2.ProductInventoryCode = r.ProductInventoryCode) cume
left join
(SELECT ProductInventoryCode, COUNT(ProductInventoryCode) AS shipped
FROM tmpDistributed s
GROUP BY s.ProductInventoryCode) s ON r.ProductInventoryCode = s.ProductInventoryCode
)
select
rs.ProductInventoryCode, rs.cumequantity, rs.QuantityInStock,
***"how to distribute"***
from rs
I'm currently using SQL Server 2008
Here's a sample screen output
The upper result is 145 Branches, below we use to distribute the ForDistributionQty field which is 3130, I am ending up with a fraction (DistVal = 21.586) which is not correct for this problem, it should be a whole number such as 21, however, if its just 21, then 21 x 145 is just 3045 which is shy of 85 units.

Answer 1

Here we distribute the values, and then make a final "adjustment" to the record which has the largest quantity (arbitrary). But at the end of the day, the math works and the distributed values are square.
Note: Not sure why in your sample why ID 2 did not get an even distribution
Declare #Table table (Id int,BranchCode int,Qty int)
Insert Into #Table values
(1, 101, 13),
(1, 102, 8),
(2, 101, 10),
(2, 102, 2),
(2, 103, 3),
(3, 101, 1),
(3, 102, 12)
Declare #Dist table (ID int,Qty int)
Insert Into #Dist values
(1,40),
(2,33),
(3,49)
;with cte0 as (
Select A.*
,ToDist = cast(D.Qty as int)
,DistVal = cast(D.Qty as int)/C.Cnt
,RN = Row_Number() over (Partition By A.ID Order By cast(D.Qty as int)/C.Cnt Desc,A.Qty Desc)
From #Table A
Join (Select ID,Cnt=count(*) from #Table Group By ID) C on A.ID=C.ID
Join #Dist D on A.ID=D.ID )
, cte1 as (
Select ID,AdjVal=Sum(DistVal)-max(ToDist) From cte0 Group By ID
)
Select A.ID
,A.BranchCode
,A.Qty
,DistVal = DistVal - case when A.RN<=abs(AdjVal) then 1*sign(AdjVal) else 0 end
From cte0 A
Join cte1 B on (A.ID=B.Id)
Order By 1,2
Returns
ID BranchCode Qty DistVal
1 101 13 20
1 102 8 20
2 101 10 11
2 102 2 11
2 103 3 11
3 101 1 24
3 102 12 25

Answer 2

If you can tolerate decimal values, a subquery seems to give a better query plan (tested on SQL 2014, with some sensible keys in place, this avoids a table spool and some additional index scans):
Declare #Table table (Id int,BranchCode int,Qty int, primary key(id, branchcode))
Insert Into #Table values
(1, 101, 13),
(1, 102, 8),
(2, 101, 10),
(2, 102, 2),
(2, 103, 3),
(3, 101, 1),
(3, 102, 12)
Declare #Dist table (ID int primary key,Qty int)
Insert Into #Dist values
(1,40),
(2,33),
(3,21)
SELECT
t.id
,t.BranchCode
,t.Qty
,(d.Qty / CAST((SELECT COUNT(*) as cnt FROM #table t2 where t.id = t2.id) AS decimal(10,2))) as DistributedQty
FROM #Table t
INNER JOIN #Dist d
ON d.id = t.Id
outputs:
Id BranchCode Qty DistributedQty
1 101 13 20.00000000000
1 102 82 20.00000000000
2 101 10 11.00000000000
2 102 21 11.00000000000
2 103 31 11.00000000000
3 101 11 10.50000000000
3 102 12 10.50000000000
If you need DistributedQty to be an int and retain remainders then I can't think of a better solution than #John Cappelletti's, noting that uneven quantities may not be as exactly even as you might hope (e.g. 32 distributed by three would result in a 12/10/10 distribution instead of an 11/11/10 distribution).