star schema designing

vinodh

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star schema designing

« on: March 02, 2010, 02:15:05 pm »

Hi ,
Iam new one to datawarehousing.How to design the star schema.
we have the hr module(OLTP) which has 77 tables.
I have some basic doubts please anyone clear that.

http://en.wikipedia.org/wiki/Star_schema

For ex.
I followed the above link.

Whether OLTP table and dimension table are same or not.
If not,can we create the dimension tables from OLTP tables?

Fact_sales table has date_id,stroe_id,product_id and units_sold.

date_id refers dim_date.
store_id refers dim_Store.
product_id refers dim_product.
but units_sold refers what?

It is a big confusion to me?please anyone help me out that?


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Sipra

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Re: star schema designing

« Reply #1 on: March 03, 2010, 01:14:10 am »

Hope you are reffering to the below diagram only

From this, other than the three foreign keys; the units sold will represent the quantity of units that have been sold by store wise, product wise and finally on which date that got sold.

This info will be retrieved absed on the three foreign keys available in the fact. Hope you have your answer..


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Re: star schema designing

« Reply #2 on: March 03, 2010, 10:35:33 am »

Quote from: vinodh on March 02, 2010, 02:15:05 pm

Fact_sales table has date_id,stroe_id,product_id and units_sold.

date_id refers dim_date.
store_id refers dim_Store.
product_id refers dim_product.
but units_sold refers what?

@Vinodh, units_sold is what is called as a "Fact".


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