Denormalization

Suppose a pharmaceutical company has a DRUG table and a table for its price changes, which is organized as follows:

DRUG (D#, Drug_Name, Drug_Type, Quantity)

PRICE (D#, StartDate, EndDate, Price)

Note that the PRICE table has a composite primary key consisting of D# and StartDate. Every order must use the order date to find out the selling price when the order was placed. The (end date + 1 ) day is equal to the StartDate of the next price for the same drug. Every report, invoice, or query will have a join between Drug and Price. Assuming that the two most recent prices are the ones that are used in 95% of transactions, find the desirable schema that could improve the performance with less redundancy.