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Why is entity relationship modeling technique not suitable for the data warehouse? How is dimensional modeling different?
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  • Dimensional Modeling (DM) is a data structure technique optimized for data storage in a Data Warehouse.
  • The purpose of dimensional modeling is to optimize the database for faster retrieval of data. The concept of Dimensional Modelling was developed by Ralph Kimball and consists of "fact" and "dimension" tables
  • Dimensional table records information an each dimension, and fact table records all the "fact", or measures.
  • A dimensional model in data warehouse is designed to read, summarise, analyse numeric information like values, balances, counts, weights, etc in a data warehouse.
  • In contrast, relation models are optimized for addition, updating and deletion of data in a real-time Online Transaction System.
  • These dimensional and relational models have their unique way of data storage that has specific advantages.
  • For instance, in the relational model, normalisation and ER models reduce redundancy in data. On the contrary, dimensional model in data warehouse arranges data in such a way that it is easier to retrieve information and generate reports.
  • Hence, Dimensional models are used in data warehouse systems and not a good fit for relational systems.
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