Calculate fixed Cost/day for multiple services on same date - sql

Question

Desired Output table T with Calculated Cost column:
SvcID Code ID Date Mins Units Cost
1 3000 15 4/4/2016 60 10 70
2 3000 17 4/4/2016 45 10 0
3 3000 15 5/2/2016 30 10 70
4 3000 18 5/2/2016 60 10 0
5 3000 10 5/2/2016 30 10 0
6 4200 16 2/1/2016 60 4 60
7 4200 9 2/1/2016 30 2 30
Query for calculating and displaying:
SELECT
...
,CASE
WHEN Code=4200 THEN Units*15
WHEN Code=3000 THEN ?
END AS Cost
FROM ...
WHERE Code IN ('3000','4200')
GROUP BY ....;
Cost should be a total of 70 for all services offered on same date for Code 3000, irrespective of number of services offered. No relation between Minutes and Units for this Code for calculating Cost.
One way could be to calculate cost as 70 for any one service and make the remaining services cost 0 for same date. Can this be done in the CASE statement?
Any better way to achieve this?

Answer 1

You need to Investigate Window functions MSDN.
Your case would become something like this:
-- New select statament
SELECT
...
,CASE
WHEN Code=4200 THEN Units*15
WHEN Code=3000 THEN ( CASE WHEN DuplicateNum = 1 THEN 70 ELSE 0 END )?
END AS Cost
FROM(
-- Your current query (with case statement removed) and ROW_NUMBER() function added
SELECT
..., ROW_NUMBER() OVER( PARTITION BY Code, Date ORDER BY ID ) AS DuplicateNum
FROM ...
WHERE Code IN ('3000','4200')
GROUP BY ....
) AS YourCurrentQuery;