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# Difference between ER-Modeling and Dimensional Modeling

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### Difference between ER-Modeling and Dimensional Modeling

1. 1. DIFFERENCE BETWEEN ER ANDDIMENTIONAL MODELINGByAbdul-rehman AslamNATIONAL UNIVERSITY OF MODERN LANGUAGESISLAMABAD25, April 20133 | P a g eAssignment
2. 2. ENTITY RELATIONSHIP MODELING (ER-Modeling):Entity-relationship modeling is a logical design technique that seeks to eliminatedata redundancy. ER models show the relationship between data. These modelsare difficult to read and understand unless trained in the model methodology.Figure 1: An example of ER-Modeling4
3. 3. 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 inherentlydimensional, and it adheres to a discipline that uses the relational model withsome important restrictions. Every dimensional model is composed of one tablewith a multipart key, called the fact table, and a set of smaller tables calleddimension tables.Figure 2: An example of Dimensional-Modeling5
4. 4. DIFFERENCES BETWEEN ER AND DM MODELING:ER-MODELING DM-MODELING A view of data from data processing. It contains both logical and physicalmodel. It process normalized data. It is utilized for OLTP databases thatuses any of the 1st or 2nd or 3rdnormal forms. It is not mapped for creatingschemas. DATA: It uses the current data. USER: More than 1000. SIZE: MB to GB. PROCESS: Normalization. DATA STORAGE: Volatile. ER-ModelingRemoves data redundancy.Ensures data consistency.Expresses relationship between theentities. A view of data from businessprocessing. It contains only a physical model. It process denormalized data. It 0is used for data warehousing anduses 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-ModelingCaptures critical measures.Views along dimensions.Useful to business users.6
5. 5. Figure 3: An example of ER-Modeling.Figure 4: An example of DM-Modeling.7
6. 6. Figure 3: An example of ER-Modeling.Figure 4: An example of DM-Modeling.7