Displaying th emean and variance of purchased items
 

Hi

i am trying to create a program using WML, WMLSCRIPT, AND JSP. The task is to create a website to be displayed in the WAP Browser. In the website for a company called 'BargainBook' that sells books and the ERD diagram for this is attached as picture (see attachement).

So now I have just finished creating a login and register page and nearly done on purchase page BUT what I want to do is to find out how to display the MEAN and VARIANCE of purchased books in a given period of time (let say 1 week for example) . Plus how can I extend my ER Diagram in order to add this because I think I may need a separate entity (or table) for this.

Any explanation will be very much appreciated. As I said I think need a new table for this BUT I do not know what kind of record should be stored on it that would help with the calculation. And also, I would like to know the suitable SQL queries to calculate the mean and variance for a given period of time.



thanks

Sorry Here Is The Attachment Erd
 

Sorry I Forgot To Put The Erd Before. Here It Is..

Re: Displaying th emean and variance of purchased items
 

You need to store the "order time" and calculate the mean/variance based on the time frame a report demands.

Re: Displaying th emean and variance of purchased items
 

The ERD needs lots of modification specially some of the relationships specially Book-BestSeller and Order-Book

Re: Displaying th emean and variance of purchased items
 

so shabir what you are trying to say is in the order entity i need tobstore time?? Ok i will try that then.

Re: Displaying th emean and variance of purchased items
 

coder zone explain what you mean by the ERD needs a lot of modification ?? HOW??/

Re: Displaying th emean and variance of purchased items
 

Yup. As you are tracking orders and need the mean and variance you need to be storing lots of time like OrderTime, DeliveryTime, ShippingTime ...

Re: Displaying th emean and variance of purchased items
 

Book and Best seller your relationship is
One Book is to many BestSeller but actually it should be BestSeller is a type of Book relationship. i.e. Is a relationship.

Book and Order relationship
It is One book many order but it should be Many Books one order.

Offtopic comment:

Re: Displaying th emean and variance of purchased items
 

I would like to add that Order should not be an entity but it should behave as a relationship between Account (Customer) and Book.Also Congrats on completing 100 posts.