Stored procedure for monthly sales with discount

I need advice on how to create a stored procedure, or many stored procedures for generating a monthly sales report in our company. I have shortened the tables down to make it more easy to understand:

We have two tables:

ITEM_SALES, which consists of:

    Item_ID
    Name
    Store
    Sales_Date
    Sales_Price
    Quantity

And ITEM_DISCOUNT, which consists of:

    Item_ID
    Name
    Store
    Sales_Price
    Date_From
    Date_To

Explanation: After each month, our different stores will send us a report on which discounts they had. These discounts can vary from one, to many days and therefor we have the Date_From, Date_to.

My idea: To make this sales report, i need a procedure that first fetches all sales in ITEM_SALES, then checks all the discounts in ITEM_DISCOUNT and overwrites the ones that have similar Item_ID, Name, and Store for a selected period.

Example: So if a item originally had a sales_price on 99,- and then had a discount sales_price to 79,- for 2014-01-02 to 2014-01-10 it has to be overwritten for that period so the report shows the right numbers.

Is this understandable? And can anyone help me or give me some tips on the way? Is temporary tables good for this?

If more info is needed, I will provide!

Solution

You can create the report by using LEFT JOIN within a Stored Procedure where month and year for which report is needed, can be passed as parameter as below:

SQL Server:

CREATE PROCEDURE GetSalesReport 
   @month INT, 
   @year  INT 
AS 
  SELECT isa.Item_ID,
         isa.Name,
         isa.Store,
         isa.Sales_Date,
         COALESCE(id.Sales_Price, isa.Sales_Price) AS SalesPrice,
         isa.Quantity
       FROM ITEM_SALES AS isa
       LEFT JOIN ITEM_DISCOUNT AS id
       ON  isa.Item_ID = id.Item_ID
       AND isa.Name = id.Name
       AND isa.Store = id.Store
       AND isa.Sales_Date BETWEEN id.Date_From AND id.Date_To 
       WHERE MONTH(isa.Sales_Date) = @month AND YEAR(isa.Sales_Date) = @year