Even splitting of a group to within 1% - sql-server-2012

Question

I have been tasked with taking a group of customers and splitting them into two equal groups for each store location. The result set requested would have the two groups for each store location within 1% of each other on customer count, within 1% of each other on order count, and within 1% of each other on amount ordered.
Below is the code I came up with and it works fairly well and most of the time it gets the desired result but sometimes(I think due to an outlier in the group) the % will be further off than 1%.
If OBJECT_ID('tempdb.dbo.#Orders') IS NOT NULL DROP TABLE #Orders
Select
StoreID
,CustomerID
,Sum(OrderID) as Orders
,Sum(OrderAmount) as AmountSold
Into #Orders
From CustomerOrders
Group by StoreID,CustomerID
IF OBJECT_ID('tempdb.dbo.#OrderRanking') IS NOT NULL DROP TABLE #OrderRanking
Select
O.*
,ROW_NUMBER() Over(Partition by StoreID Order by AmountSold, Orders) as Ranking
Into #OrderRanking
From #Orders as O
Select
R.StoreID
,Count(CustomerID) as CustomerCount
,Sum(R.Orders) as Orders
,Sum(R.AmountSold) as Amountsold
,Case When Ranking%2 = 0 Then 'A' Else 'B' End as 'Grouping'
From #OrderRanking as R
Group by
R.StoreID
,Case When Ranking%2 = 0 Then 'A' Else 'B' End
Is there a better way to split the groups to ensure the 1% variance? Or maybe a way to loop through several different splits until it finds a 1%? If looping would need a fail safe to prevent infinite loop in case of impossible split something like after x loops just take closest split.
I am using SQL Server 2012 and SSMS 2016. Thanks for any help you can provide.
Edit:
I had tried to convert the code into something not company specific I messed up the code. I realized that and adjusted the code to show what is truly being sought after.
Edit2: I made some progress on my own and wanted to update the question.
So I was working on this some more and I was able to get it to sort on a random order each time you run the code and have it display the Variance for each of the groups. Now all I want to add is a way to loop through X number times and keep the one that has lowest overall variance. This weekend I might try a few more things. But for now below is the new code I spoke of.
If OBJECT_ID('tempdb.dbo.#Orders') IS NOT NULL DROP TABLE #Orders
Select
StoreID
,CustomerID
,Sum(OrderID) as Orders
,Sum(OrderAmount) as AmountSold
,Rand() as Random
Into #Orders
From CustomerOrders
Group by StoreID,CustomerID
IF OBJECT_ID('tempdb.dbo.#OrderRanking') IS NOT NULL DROP TABLE #OrderRanking
Select
O.*
,ROW_NUMBER() Over(Partition by StoreID Order by Random) as Ranking
Into #OrderRanking
From #Orders as O
If OBJECT_ID('tempdb.dbo.#Split') IS NOT NULL DROP TABLE #Split
Select
R.StoreID
,Count(CustomerID) as CustomerCount
,Sum(R.Orders) as Orders
,Sum(R.AmountSold) as Amountsold
,Case When Ranking%2 = 0 Then 'A' Else 'B' End as 'Grouping'
Into #Split
From #OrderRanking as R
Group by
R.StoreID
,Case When Ranking%2 = 0 Then 'A' Else 'B' End
Select
S.StoreID
,((Cast(Max(Case When S.[Grouping] = 'A' Then S.CustomerCount Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.CustomerCount Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.CustomerCount Else 0 End) as decimal(18,2)))*100 as CustomerCountVar
,((Cast(Max(Case When S.[Grouping] = 'A' Then S.Orders Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.Orders Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.Orders Else 0 End) as decimal(18,2)))*100 as OrderVar
,((Cast(Max(Case When S.[Grouping] = 'A' Then S.Amountsold Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.Amountsold Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.Amountsold Else 0 End) as decimal(18,2)))*100 as AmountsoldVar
From #Split as S
Group by S.StoreID

Answer 1

So it is truly impossible to always get within 1% as we all expected but like I said we were ok with trying to get as close as possible after X number of tries. I have figured out how to make this happen. Below is the code I used currently set at 10 tries but can be changed to whatever number works for the business.
If OBJECT_ID('tempdb.dbo.#TestB') IS NOT NULL DROP TABLE #TestB
Create Table #TestB
(
StoreID int
,CustomerID VarChar(11)
,Orders int
,AmountSold Float
,Random Float
,Ranking bigint
,CombinedVar Decimal(18,2)
)
If OBJECT_ID('tempdb.dbo.#BestPrep') IS NOT NULL DROP TABLE #BestPrep
Create Table #BestPrep
(
StoreID int
,CustomerID VarChar(11)
,Orders int
,AmountSold Float
,Random Float
,Ranking bigint
,CombinedVar Decimal(18,2)
)
Declare #Giveup int
Set #GiveUp = 10
WHILE #GiveUp > 0
BEGIN
If OBJECT_ID('tempdb.dbo.#Orders') IS NOT NULL DROP TABLE #Orders
Select
StoreID
,CustomerID
,Sum(OrderID) as Orders
,Sum(OrderAmount) as AmountSold
,Rand() as Random
Into #Orders
From CustomerOrders
Group by StoreID,CustomerID
IF OBJECT_ID('tempdb.dbo.#OrderRanking') IS NOT NULL DROP TABLE #OrderRanking
Select
O.*
,ROW_NUMBER() Over(Partition by StoreID Order by Random) as Ranking
Into #OrderRanking
From #Orders as O
If OBJECT_ID('tempdb.dbo.#Split') IS NOT NULL DROP TABLE #Split
Select
R.StoreID
,Count(CustomerID) as CustomerCount
,Sum(R.Orders) as Orders
,Sum(R.AmountSold) as Amountsold
,Case When Ranking%2 = 0 Then 'A' Else 'B' End as 'Grouping'
Into #Split
From #OrderRanking as R
Group by
R.StoreID
,Case When Ranking%2 = 0 Then 'A' Else 'B' End
If OBJECT_ID('Tempdb.dbo.#Var') IS NOT NULL DROP TABLE #Var
Select
S.StoreID
,ABS(((Cast(Max(Case When S.[Grouping] = 'A' Then S.CustomerCount Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.CustomerCount Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.CustomerCount Else 0 End) as decimal(18,2)))*100) as CustomerCountVar
,ABS(((Cast(Max(Case When S.[Grouping] = 'A' Then S.Orders Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.Orders Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.Orders Else 0 End) as decimal(18,2)))*100) as OrderVar
,ABS(((Cast(Max(Case When S.[Grouping] = 'A' Then S.Amountsold Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.Amountsold Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.Amountsold Else 0 End) as decimal(18,2)))*100) as AmountsoldVar
,ABS(((Cast(Max(Case When S.[Grouping] = 'A' Then S.Orders Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.Orders Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.Orders Else 0 End) as decimal(18,2)))*100)
+
ABS(((Cast(Max(Case When S.[Grouping] = 'A' Then S.Amountsold Else 0 End) as decimal(18,2))-Cast(Max(Case When S.[Grouping] = 'B' Then S.Amountsold Else 0 End) as decimal(18,2)))
/ Cast(Max(Case When S.[Grouping] = 'B' Then S.Amountsold Else 0 End) as decimal(18,2)))*100) as CombinedVar
INTO #Var
From #Split as S
Group by S.StoreID
If Exists (Select * From #Var Where (OrderVar < 1 and AmountSoldVar <1) Or CombinedVar < 2)
If Object_ID('tempdb.dbo.#TestA') IS NOT NULL DROP TABLE #TestA
Select
A.StoreID
,A.CustomerID
,A.Orders
,A.AmountSold
,A.Random
,A.Ranking
,V.CombinedVar
Into #TestA
From #OrderRanking as A
Join #var as V
on A.StoreID = V.StoreID
Where A.StoreID in
(Select StoreID From #Var Where (OrderVar < 1 and AmountSoldVar <1) Or CombinedVar < 2)
Insert Into #TestB
Select
A.StoreID
,A.CustomerID
,A.Orders
,A.AmountSold
,A.Random
,A.Ranking
,A.CombinedVar
From #TestA as A
Left Join #TestB as B
on A.CustomerID = B.CustomerID
Where
B.CustomerID is null
Insert Into #BestPrep
Select
A.StoreID
,A.CustomerID
,A.Orders
,A.AmountSold
,A.Random
,A.Ranking
,V.CombinedVar
From #OrderRanking as A
Join #Var as V
on A.StoreID = V.StoreID
Left Join #BestPrep as B
on A.CustomerID = B.CustomerID
and V.CombinedVar > B.CombinedVar
Where
B.CustomerID is null
Set #Giveup = #Giveup-1
END
If Object_ID('tempdb.dbo.#bestPrep2') IS NOT NULL DROP TABLE #bestPrep2
Select
A.StoreID
,Min(CombinedVar) as CombinedVar
Into #BestPrep2
From #BestPrep as A
Group by
A.StoreID
Select A.*
From #BestPrep as A
Join #BestPrep2 as B
on A.StoreID = B.StoreID
and A.CombinedVar = B.CombinedVar
Union
Select * From #TestB