Chapter 14 Flashcards
What are 4 steps to convert entity relationship model to dimensional model
1- Choose the business process
2- Choose the grain
3- Choose the facts
4- Choose the dimensions
What is grain
It tells the level of detail in table. If grain is highers then details will be higher and if rain is lower then detail will be less. We can say it is fundamental atomic level of data. And its a unit of transaction.
What is fact
It is a numeric value and it is non-key
Does dimension tables are smaller in size and larger in numbers
Yes and they tend to create star schema.
What is business process
Business process is a major operational process in an organization (e.g. orders, invoices, inventory)
What terminology used for business process
Data mart
What terminology used for grain
Unit of analysis
Is aggregation irreversible
Yes
What is fact and dimension in following statement
“We need monthly sales volume and Rs. by week, product and zone”
fact: sales volume, rupees
dimension: week, product, zone
Does dimension can have hierarchy
Yes
What is dimension
The single valued attributes (which value does not change) during recording of a transaction is dimension
Can dimension be multi-valued
Yes. For example car maintenance (oil change, brake oil change, service)
