How add up values from multiple SQL columns based on occurrances - sql

Question

I need select values from a table and returns the total hours for all categories and their occurrences. The challenge is that there are different totals for each occurrence.
My query:
SELECT c.Category,
c.HrsFirstOccur,
c.HrsAddlOccur,
COUNT(*) AS Occurrences
FROM dbo.Categories sc
INNER JOIN dbo.Categories c
ON sc.CategoryID = c.CategoryID
INNER JOIN dbo.OrderHistory oh
ON sc.GONumber = oh.OrderNumber
AND sc.Item = oh.ItemNumber
WHERE sc.BusinessGroupID = 1
AND oh.OrderNumber = 500
AND oh.ItemNumber = '100'
GROUP BY c.Category, c.HrsFirstOccur, c.HrsAddlOccur
returns the following results:
Category
HrsFirstOccur
HrsAddlOccur
Occurrences
Inertia
24
16
2
Lights
1
0.5
4
Labor
10
0
1
The total is calculated based on the number of occurrences. The first one is totaled then for each additional occurrence, the HrsAddlOccur is used.
My final result should be (24 + 16) + (1 + 0.5 + 0.5 + 0.5) + 10 for a grand total of 52.5.
How do I loop and process the results to total this up?

Answer 1

The total is calculated based on the number of occurrences. The first one is totaled then for each additional occurrence, the HrsAddlOccur is used.
SQL databases understand arithmetic. You can perform the computation on each row. As I understand, the logic you want is:
SELECT
c.Category,
c.HrsFirstOccur,
c.HrsAddlOccur,
COUNT(*) AS Occurrences,
c.HrsFirstOccur + ( COUNT(*) - 1 ) * HrsAddlOccur As Total
FROM ... < rest of your query > ..
Later on you can aggregate the whole resultset to get the grand total:
SELECT SUM(Total) GrandTotal
FROM (
... < above query > ..
) t

Answer 2

you can sum them simply up
WITH CTE as(SELECT c.Category,
c.HrsFirstOccur,
c.HrsAddlOccur,
COUNT(*) AS Occurrences
FROM dbo.Categories sc
INNER JOIN dbo.Categories c ON sc.CategoryID = c.CategoryID
INNER JOIN dbo.OrderHistory oh ON sc.GONumber = oh.OrderNumber
AND sc.Item = oh.ItemNumber
WHERE sc.BusinessGroupID = 1
AND oh.OrderNumber = 500
AND oh.ItemNumber = '100')
SELECT SUM(HrsFirstOccur + (CAST((Occurrences -1) AS DECIMAL(8,2)) * HrsAddlOccur)) as total FROM CTE
it would do it like the example
CREATE TABLE CTE
([Category] varchar(7), [HrsFirstOccur] int, [HrsAddlOccur] DECIMAL(8,2), [Occurrences] int)
;
INSERT INTO CTE
([Category], [HrsFirstOccur], [HrsAddlOccur], [Occurrences])
VALUES
('Inertia', 24, 16, 2),
('Lights', 1, 0.5, 4),
('Labor', 10, 0, 1)
;
3 rows affected
SELECT SUM(HrsFirstOccur + (CAST((Occurrences -1) AS DECIMAL(8,2)) * HrsAddlOccur)) as total
FROM CTE
total
52.5000
fiddle