Getting the max and the min paid departments - sql-server

Question

I have the following query :
SELECT D.Dept,(SUM(D.AMOUNT) /SUM(A.AMOUNT)) AS Res
FROM Dept AS D
INNER JOIN Charge AS A ON D.DeptId=A.DeptId
GROUP BY D.Dept
Input :
Dept table :
Dep Amount
1 300
1 300
2 1000
3 3000
Charge table :
Dep Charge
1 150
1 150
2 200
3 300
I want to calculate the sum of the amount of the salaries for each department and divide it by the charges of each department
I want to have the dept having the max and the dept having the min like below :
Dept Res
3 10
2 5
1 2
To select the max and the min dept :
Dept Res
3 10
1 2

Answer 1

We can use a CTE with 2 RANK ordered in opposite ways and then get the first in each direction to get the mini et maxi
create table Dept (Dept int, Amount int);
insert into dept values
(1, 200),
(1, 345),
(2, 690),
(3, 3000);
create table Charge (Dept int, Amount int);
insert into Charge values
(1, 568),
(1, 657),
(2, 300),
(3, 300);
SELECT
D.Dept,
SUM(D.AMOUNT) Salaries,
SUM(A.AMOUNT) Expenses,
round((1e* SUM(D.AMOUNT) /SUM(A.AMOUNT)),2) AS Res
FROM Dept AS D
JOIN Charge AS A ON D.Dept=A.Dept
GROUP BY D.Dept
ORDER BY (1e* SUM(D.AMOUNT) /SUM(A.AMOUNT)) DESC
Dept | Salaries | Expenses | Res
---: | -------: | -------: | ---:
3 | 3000 | 300 | 10
2 | 690 | 300 | 2.3
1 | 1090 | 2450 | 0.44
with allDepts as(
SELECT
D.Dept,
rank() over ( order by (1e* SUM(D.AMOUNT) /SUM(A.AMOUNT)) DESC) maxi,
rank() over (order by (1e* SUM(D.AMOUNT) /SUM(A.AMOUNT)) asc) mini,
round((1e* SUM(D.AMOUNT) /SUM(A.AMOUNT)),2) AS Res
FROM Dept AS D
JOIN Charge AS A ON D.Dept=A.Dept
GROUP BY D.Dept
)
select
Dept, Res
from allDepts
where maxi = 1
or mini = 1;
Dept | Res
---: | ---:
1 | 0.44
3 | 10
db<>fiddle here

Answer 2

You can aggregate and join each query as a derived table, derive the max and min values using a windowed aggregate, then filter:
with r as (
select d.Dept, d.Amount / c.Amount Res,
Min(d.Amount / c.Amount) over() MinAmount,
Max(d.Amount / c.Amount) over() MaxAmount
from (
select dept, Sum(Amount) Amount
from Dept
group by Dept
)d join (
select dept, Sum(Amount) Amount
from Charge
group by Dept
) c on c.Dept=d.Dept
)
select Dept, Res
from r
where Res in (MinAmount, MaxAmount);
Demo Fiddle

Answer 3

First aggregate both in sub-queries.
This gets a 1-on-1 relationship on the DeptId.
Then to get the MIN/MAX Res you can use ROW_NUMBER or DENSE_RANK.
SELECT DeptId, Res
FROM
(
SELECT D.DeptId, DeptAmount, ChargeAmount
, CAST(1.0*DeptAmount/NULLIF(ChargeAmount, 0) AS INT) AS Res
, DENSE_RANK() OVER (ORDER BY 1.0*DeptAmount/NULLIF(ChargeAmount, 0) ASC) AS RNK_ASC
, DENSE_RANK() OVER (ORDER BY 1.0*DeptAmount/NULLIF(ChargeAmount, 0) DESC) AS RNK_DESC
FROM (
SELECT DeptId, SUM(Amount) AS DeptAmount
FROM Dept
GROUP BY DeptId
) D
INNER JOIN (
SELECT DeptId, SUM(Charge) AS ChargeAmount
FROM Charge
GROUP BY DeptId
) C ON C.DeptId = D.DeptId
) Q
WHERE (RNK_ASC = 1 OR RNK_DESC = 1)
ORDER BY RNK_DESC;
DeptId | Res
-----: | --:
3 | 10
1 | 2
Test on db<>fiddle here