sql Query on effective date - sql

Question

I would like to get report for drink purchased in whole month but price of the drink can change any time in month and I would like to get report for a month with price change
I have two tables
SELECT [ID]
,[DrinkID]
,[UserID]
,[qty]
,[DateTaken]
FROM [Snacks].[dbo].[DrinkHistory]
SELECT [ID]
,[DrinkID]
,[UserID]
,[qty]
,[DateTaken]
FROM [Snacks].[dbo].[DrinkHistory]
[DrinkHistory]:
ID DrinkID UserID qty DateTaken
----------------------------------------------------------------------
1 1 1 1 2014-05-10
2 1 1 2 2014-05-15
3 2 1 1 2014-06-01
4 2 1 4 2014-06-01
5 1 1 3 2014-05-20
6 1 1 4 2014-05-30
[DrinkPricesEffect]:
PriceID DrinkID DrinkPrice PriceEffectiveDate IsCurrent
-----------------------------------------------------------------------------------
1 1 10.00 2014-05-01 1
2 1 20.00 2014-05-20 1
3 2 9.00 2014-06-01 1
4 2 8.00 2014-01-01 1
5 1 30.00 2014-05-25 1
6 1 40.00 2014-05-28 1
I would like to have result as under date taken between 2014-05-1 to 2014-05-31
DrinkId Qty Price DateTaken PriceEffectiveDate
-----------------------------------------------------------------------
1 1 10 2014-05-10 2014-05-01
1 2 10 2014-05-15 2014-05-01
1 3 20 2014-05-20 2014-05-20
1 4 40 2014-05-30 2014-05-28
Is there any who can give me some idea or write query for me?

Answer 1

If your drink price can change any time in a month you could additionaly save the price for each purchase. I would add a column [PricePaid] to the table [DrinkHistory].
When adding a record to [DrinkHistory], the price for the drink at the moment is known, but later it might change so you save the current price to the history...
Then for your result you could just display the Whole [DrinkHistory]
SELECT * FROM DrinkHistory;

Answer 2

This should work:
Select
DH.DrinkId,
DH.Qty,
DPE.DrinkPrice AS Price,
DH.DateTaken,
DPE.PriceEffectiveDate
FROM DrinkHistory DH
JOIN DrinkPricesEffect DPE ON DPE.PriceID =
(
Select Top 1 PriceID FROM
(
Select PriceID,RANK() OVER(ORDER BY PriceEffectiveDate DESC ) AS rnk
FROM DrinkPricesEffect
WHERE DH.DrinkId = DrinkId AND
DH.DateTaken >= PriceEffectiveDate
)SubQ WHERE rnk = 1
)
WHERE DH.DateTaken Between '2014-05-01' AND '2014-05-30'
Here you can find the SQL Fiddle link: http://sqlfiddle.com/#!6/5f8fb/26/0