Displaying th emean and variance of purchased items

chickenyd's Avatar, Join Date: Mar 2006
Light Poster
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
0
chickenyd's Avatar, Join Date: Mar 2006
Light Poster
Sorry I Forgot To Put The Erd Before. Here It Is..
Attached Images
File Type: jpg er_bookshop_4.jpg (27.4 KB, 8 views)
0
shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
You need to store the "order time" and calculate the mean/variance based on the time frame a report demands.
0
coderzone's Avatar, Join Date: Jul 2004
Team Leader
The ERD needs lots of modification specially some of the relationships specially Book-BestSeller and Order-Book
0
chickenyd's Avatar, Join Date: Mar 2006
Light Poster
so shabir what you are trying to say is in the order entity i need tobstore time?? Ok i will try that then.
0
chickenyd's Avatar, Join Date: Mar 2006
Light Poster
coder zone explain what you mean by the ERD needs a lot of modification ?? HOW??/
0
shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Quote:
Originally Posted by chickenyd
so shabir what you are trying to say is in the order entity i need tobstore time?? Ok i will try that then.
Yup. As you are tracking orders and need the mean and variance you need to be storing lots of time like OrderTime, DeliveryTime, ShippingTime ...
0
coderzone's Avatar, Join Date: Jul 2004
Team Leader
Quote:
Originally Posted by chickenyd
coder zone explain what you mean by the ERD needs a lot of modification ?? HOW??/
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:
Hey thats my Post No 100

Last edited by coderzone; 12Mar2006 at 22:17..
0
shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Quote:
Originally Posted by coderzone
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.
I would like to add that Order should not be an entity but it should behave as a relationship between Account (Customer) and Book.
Quote:
Originally Posted by coderzone
Offtopic comment:
Hey thats my Post No 100
Also Congrats on completing 100 posts.