Sql Server - Get SUM() of values for only Active Users - sql-server

Question

I have a requirement where i need to get Total Active Employees and Total Sales by RegionId
My query result should be like below.
RegionId | TotalEmployees | TotalSales | Average
1 10 100 10
2 3 15 5
My front end application will pass all the RegionIds as a single string separated by a comma, my query parameter is of type VARCHAR() and the Input paramter will look like '1,2,3,4,7,14,26' and there can be upto 20 Region Ids in a single string separated by a comma.
SELECT E.[RegionId] as RegionId
,COUNT(E.[EmployeeId) AS TotalEmployees
,(SELECT SUM([Sale])
FROM dbo.[Sales]
WHERE RegionId = R.[RegionId]
) AS TotalSales
,TotalSales/TotalEmployees AS Average
FROM dbo.[Employee]
JOIN [dbo].[ufn_StringSplit](#RegionIdCollection, ',') RegionId
ON E.RegionId = CAST(RegionId.[Data] AS Varchar(5000))
WHERE E.[Active] = 1
GROUP BY E.[RegionId]
My Employee table structures look alike below
EmployeeId | Name | RegionId | Active
100 Tom 2 1
101 Jim 4 0
103 Ben 2 1
Sales Table
SaleId | EmployeeId| RegionId | Sale
1 100 2 3500
2 101 4 2000
3 100 2 1500
Now my issue is when i am getting TotalSales the below query gets all the sales by RegionId, but i need to get All the sales done by only current Active employees in the Employee table
(SELECT SUM([Sale])
FROM dbo.[Sales]
WHERE RegionId = R.[RegionId]
) AS TotalSales

Answer 1

There is no reason to use a sub-select to find the sum of sales here, that will result in running that query for each and every row. You want to aproach this in a set based way which means you need to join and group appropriately:
with s as
(
select e.RegionId
,e.EmployeeId
,sum(s.Sale) as EmployeeSales
from dbo.ufn_StringSplit(#RegionIdCollection, ',') as r
join dbo.Employee as e
on r.RegionId = CAST(r.[Data] AS varchar(20)) -- Do you really need 5000 characters here?
left join dbo.Sales as s
on r.RegionId = s.RegionId
and e.EmployeeId = s.EmployeeId
where e.Active = 1
group by e.RegionId
,e.EmployeeId
)
select s.RegionId
,count(s.EmployeeId) as TotalEmployees
,sum(s.EmployeeSales) as TotalSales
,sum(s.EmployeeSales)/count(s.EmployeeId) as Average
from s
group by s.RegionId