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
chickenyd's Avatar, Join Date: Mar 2006
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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)
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.
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
chickenyd's Avatar, Join Date: Mar 2006
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so shabir what you are trying to say is in the order entity i need tobstore time?? Ok i will try that then.
chickenyd's Avatar, Join Date: Mar 2006
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coder zone explain what you mean by the ERD needs a lot of modification ?? HOW??/
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 ...
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..
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.