SQL Server Overall Total in a group by - sql-server

Question

In my SQL Server Query, I am trying to count the number of employees per site. This works, but when I try to add in a percentage of total, it still groups by Site so it is inaccurate.
Is there an easier way to achieve this?
I am using this Query to create a view.
select Site.SiteName,
sum(case when Employee.ActiveStatus = 'Yes' then 1 else 0 end) as
"NumberOfEmployees",
CONVERT(decimal(6,2),(sum(case when Employee.ActiveStatus = 'Yes' then 1
else 0 end))/(convert(decimal(6,2),COUNT(EmployeeID)))) as PercentageOfEmps
from Employee
left join Site
on(Employee.SiteID=Site.SiteID)
GROUP BY Site.SiteName;
GO

Answer 1

You could use subquery:
select
Site.SiteName,
NumberOfEmployees = sum(case when Employee.ActiveStatus = 'Yes' then 1 else 0 end),
PercentageOfEmps = CONVERT(decimal(6,2),(sum(case when Employee.ActiveStatus = 'Yes' then 1
else 0 end))/(SELECT COUNT(EmployeeID) FROM Employee)
from Employee
left join Site
on Employee.SiteID=Site.SiteID
GROUP BY Site.SiteName;

Answer 2

I can't provide an answer for your scenario, as I don't have any sample data to use, therefore I've provided a small dataset.
One method is to use a CTE/Subquery to get a total number and then include the total in the GROUP BY. This method avoids 2 scans of the table:
WITH VTE AS(
SELECT *
FROM (VALUES(1,'Steve',1),
(2,'Jayne',1),
(3,'Greg',2),
(4,'Sarah',3)) V(EmpID, EmpName, SiteID)),
CTE AS(
SELECT V.EmpID,
V.EmpName,
V.SiteID,
COUNT(V.EmpID) OVER () AS TotalCount
FROM VTE V)
SELECT C.SiteID,
COUNT(C.EmpID) AS Employees,
COUNT(C.EmpID) / (C.TotalCount *1.0) AS Perc
FROM CTE C
GROUP BY C.SiteID,
C.TotalCount;

Answer 3

This script should help-
SELECT
Site.SiteName,
COUNT(EmployeeID) AS [NumberOfEmployees],
((COUNT(EmployeeID)*1.0)/(SELECT COUNT(*) FROM Employee WHERE ActiveStatus = 'Yes'))*100.00 as PercentageOfEmps
FROM Employee
INNER JOIN Site
ON Employee.SiteID = Site.SiteID
WHERE Employee.ActiveStatus = 'Yes'
GROUP BY Site.SiteName;

Answer 4

Data creation script
declare #Employee Table(EmployeeID int ,ActiveStatus nvarchar(20) ,SiteID int)
declare #Site Table(SiteName nvarchar(20) ,SiteID int)
insert into #Employee values(1,'Yes',101),(2,'Yes',101),(3,'Yes',102),(4,'Yes',102),
(5,'Yes',101)
insert into #Site values('Site1',101)
insert into #Site values('Site2',102)
//real script to get the %percentage
;with cte as
(
select s.SiteName,sum(case when e.ActiveStatus = 'Yes' then 1 else 0 end) as "NumberOfEmployees"
from #Employee e
left join #Site s
on(e.SiteID=s.SiteID)
GROUP BY s.SiteName
),
cte_sum as
(select sum(NumberOfEmployees) as total from cte )
select c.*, convert (decimal(6,2),c.NumberOfEmployees)/convert (decimal(6,2),cs.total)*100 from cte_sum cs, cte c;