pal.amol

 Profile Answers by pal.amol 

• Feb 27th, 2008

 

Dimensional modelling sometimes mistaken as the ER modelling but no it is wrong, DM is just modelling which is more flexible for the user perspective.
In ER it is not mapped unlike DM for creating schemas and  moreover it does not also act to convert normalize data in to denormalize form.

Basicalling aim of modelling data is for retrieving the data fast when user will be querying  , so it happens in DM like star schema.

raj_infadev

 Profile Answers by raj_infadev 

• Oct 13th, 2008

 

Modeling is nothing but designing the database by using any Database Normalization techniques (1NF, 2NF, 3NF.......etc)

Data Modeling is having 2 types:

1. ER Modeling
2. Dimensional Modeling

ER Modeling is for OLTP databases uses any of the forms 1NF or 2NF or 3NF. Contains Normalized data

Dimensional Modeling is for Datawarehouses uses 3NF. Contains denormalized data.

The only difference between these 2 modeling techniques is the Normalization Form used to design the databases. Both modeling techniques are represented using ER diagrams. So, depends upon the client requirement it should be decided...

Regards
Raj

Sharat

• Jan 5th, 2015

 

Raj, 1NF is highly denormalized and the higher forms are more normalized. You said Dimensional Modeling is for datawarehouses and uses 3NF. Contains denormalized data. 3NF is highly normalized and how can the datawarehouses can have denormalized data

Manjunath

• Apr 9th, 2015

 

both Dim Modeling and ER modeling can be 3NF, which is highly normalized, As raj mentioned ER is used for OLTP and DM for OLAP. in both the cases data is stored in a set of tables and related to each other through PK and FK. the difference lies in what fields as stored in what table.

In case of OLTP all the fields which represent the characteristics of an entity are stored in one table, where as in DM all the fields defining each dimension are stored in each table.