Sql query to calculate total based on 2 conditions in 1 query

Question

I have a table like below:

Employee : 

EmpNo
FirstName
LastName

Dept : 

DeptName
Head
NoOfEmployees

EmpContracts : 

EmpNo  DeptName   Salary    StartDate     EndDate
1      d1         1000      2017-12-12    2018-12-12
1      d2         1000      2017-06-12    2018-12-12
2      d3         1000      2017-06-12    2018-12-12
2      d4         1000      2017-12-12    2018-12-12     
3      d5         4000      2017-12-12    2018-12-12

This is what I am trying to do:

Display the dept details and the total salary amount for the contracts on each department, with the following conditions: 1) Calculated total for contracts must be from employees that work exclusively for that department 2) Total calculated for the contracts should be after 2001 order result by NoOfEmployees

I am confused with how to satisfy both condition in 1 query?

This is what I have tried so far:

select [EmpNO],[DeptName],[StartDate], SUM([Salary]) from [dbo].[EmpContracts]
group by [EmpNo],[DeptName],[StartDate]
having YEAR([StartDate]) > 2001

Can anybody please help me with this?

Answer 1

I am not sure but here it is:

select EmpNO, max(DeptName), SUM(Salary) total_sal
from EmpContracts 
where year(StartDate) > 2001
group by EmpNo
having count(distinct DeptName) =1;

Here is a DEMO