Calculate sum in tier pricing. SQL Server. Tier pricing table - sql

Question

I am having trouble with my sum query in SQL Server.
I have a tier price table set up like. The name of the table is called TierPricing.
CID RangeID MinValue MaxValue Price Class
1 1 1 5 1.50 1
2 2 6 10 1.25 1
3 3 11 999999999 1.00 1
.
I have a query of
DECLARE #QuantityEntered int
DECLARE #ClassEntered int
SET #QuantityEntered = 10;
SET #ClassEntered = 1
SELECT IIf(#QuantityEntered>=TierPricing.MaxValue,TierPricing.MaxValue*TierPricing.Price,(#QuantityEntered-(TierPricing.MinValue-1))*TierPricing.Price)) AS RangePrice
FROM
TierPricing
WHERE
(((TierPricing.MinValue)<=#QuantityEntered) AND ((TierPricing.Class)=#ClassEntered));
The problem arises when I use the value of 10 for #QuantityEntered. Instead of returning 13.75 it returns 20.00 and I cant figure out why. From the table from value 9 to 10 should increase by 1.25 from 12.50 to 13.75.
Further Explanation.
#QuantityEntered = 1 returns 1.50 because 1 falls in between 1 and 5 and 1.50 is added from price field for a total of 1.50
#QuantityEntered = 2 returns 3.00 because 2 falls in between 1 and 5 and 1.50 is added from price field for total of 3.00
#QuantityEntered = 3 returns 4.50 because 3 falls in between 1 and 5 and 1.50 is from price field added for total of 4.50
#QuantityEntered = 4 returns 6.00 because 4 falls in between 1 and 5 and 1.50 is from price field added for total of 6.00
#QuantityEntered = 5 returns 7.50 because 5 falls in between 1 and 5 and 1.50 is from price field added for total of 7.50
#QuantityEntered = 6 returns 8.75 because 6 falls in between 6 and 10 and 1.25 is from price field added for total of 8.75
#QuantityEntered = 7 returns 10.00 because 7 falls in between 6 and 10 and 1.25 is from price field added for total of 10.00
#QuantityEntered = 8 returns 11.25 because 8 falls in between 6 and 10 and 1.25 is from price field added for total of 11.25
#QuantityEntered = 9 returns 12.50 because 9 falls in between 6 and 10 and 1.25 is from price field added for total of 12.50
#QuantityEntered = 10 Should return 13.75 but returns 20.00
What I am doing wrong with my query?

Answer 1

I was trying to solve this problem myself when I found your question. I figured out a set based way to get the correct result, but you have to change your Min and Max values to start from 0 and start from the lower tier's end. So the tiers are now 0-5, 5-10, and 10 - 999999999. Here is a recreation of your problem:
create table #TierPricing
(
CID int
,RangeId int
,MinValue int
,MaxValue int
,Price money
,Class int
)
insert into #TierPricing(CID, RangeId, MinValue, MaxValue, Price, Class) values (1,1,0,5,1.50,1)
insert into #TierPricing(CID, RangeId, MinValue, MaxValue, Price, Class) values (2,2,5,10,1.25,1)
insert into #TierPricing(CID, RangeId, MinValue, MaxValue, Price, Class) values (3,3,10,999999999,1.00,1)
DECLARE #QuantityEntered int
DECLARE #ClassEntered int
SET #QuantityEntered = 10;
SET #ClassEntered = 1
;with t as (
select
#TierPricing.*
,case
when #QuantityEntered > MaxValue then MaxValue - MinValue --The #QuantityEntered fills up the entire tier
when #QuantityEntered > MinValue then #QuantityEntered - MinValue --The #QuantityEntered partillay fills the tier
else 0
end as TierQuantity
from #TierPricing
)
select
sum(TierQuantity * Price) as RangePrice
from t
drop table #TierPricing
This will return 13.75 when #QuantityEntered is set to 10.