Difference between ER-Modeling and Dimensional Modeling

1. ENTITY RELATIONSHIP MODELING (ER-Modeling):
Entity-relationship modeling is a logical design techniquethat seeks to eliminate data
redundancy. ER models show the relationship between data. These models are difficult
to read and understand unless trained in the modelmethodology.





Figure1: An example of ER-Modeling

2. DIMENSIONAL MODELING (DM-Modeling):
DM is a logical design technique that seeks to present the data in a standard, intuitive
framework that allows for high-performance access. It is inherently dimensional, and it
adheres to a discipline that uses the relational model with some important restrictions.
Every dimensional model is composed of one table with a multipart key, called the fact
table, and a set of smaller tables called dimension tables.


Figure 2: An example of Dimensional-Modeling

3. DIFFERENCES BETWEEN ER AND DM MODELING:

ER-MODELING

DM-MODELING


 A view of data from data processing.
 It contains both logical and physical
model.
 Itprocess normalized data.
 It is utilized for OLTP databases that
uses any of the 1st or 2nd or 3rd
normal forms.
 It is not mapped for creating
schemas.
 DATA:It uses the current data.
 USER:More than 1000.
 SIZE:MB to GB.
 PROCESS: Normalization.
 DATA STORAGE: Volatile.
 ER-Modeling
Removes data redundancy.
Ensures data consistency.
Expresses relationship between the
entities.



 A view of data from business
processing.
 It contains only a physical model.
 It process denormalized data.
 It 0is used for data warehousing and
uses 3rd normal form.
 It is mapped for creating schemas.
 DATA:It uses the historical data.
 USER:Using only top management.
 SIZE: GB to Tb.
 PROCESS:Denormalization.
 DATA STORAGE:Non Volatile.
 DM-Modeling
Captures critical measures.
Views along dimensions.
Useful to business users.

4. Figure 3: An example of ER-Modeling.



Figure 4: An example of DM-Modeling.