Friday, January 14, 2011

What is Fact Dimension?

Sometimes we need to analyze our data based on the some specific value which are available only at fact table. In this case, the particular data will act as a dimension. This dimension is called as Fact Dimension.

Fact Dimension also known as Degenerated Dimension

Fact Dimension will be more helpful, when we need to categorize the data based on similar kinds of data.

Example: Invoice Number, Purchase Order No, Etc.,

Of course, we can maintain separate dimension table instead of using Fact Dimensions, but no benefit, because the dimension table grow in the same ratio of fact table growth. So by creating Fact dimension, we can avoid duplicate data and reducing memory consumption. Also it helps to improve the performance during data retrieval time.

Wednesday, December 29, 2010

Data modelling Vs Dimensional modelling

Data modelling:
Modelling data storage optimized for Transactional Processing is Data Modelling

Dimensional modelling:
Modelling data storage optimized for Analytical Processing is Dimension Modelling..

SSAS: What is Named Query?

1. Named Query is a SQL Statements and it act as a another table

2. It is formed by selecting rows and columns from single tables or relating multiple tables

3. It helps to make the data source view with new table structure without modifying the underlying data source

SSAS: What is Linked Dimension ?

In SQL Server Analysis Services (SSAS), Linked Dimension is a dimension which is existed in other analysis services DB. It may exist in same or different server. it helps the user to keep the common dimension in multiple database.

Tuesday, December 28, 2010

What is Conformed dimension?

Conformed dimension is a dimension that has a single meaning or content throught datawarehouse.we can use it accross the fact tables


Example: Time, Product, Staff Dimensions are Conformed dimension, it is shared across multiple fact tables.


What is Role Playing dimension?

Role Playing dimension is a dimension, it can play different roles in a fact table depending on the context.

For example: Date dimension

Date dimension can be used for ordered date, shipping date, shipment date, and invoice date, etc., in an order line fact.

In the data warehouse, you will have a single dimension table for the dates. You will have multiple warehouse foreign key from the fact table to teh same dimension.