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Data Warehousing Concepts


What is data warehouse? Difference between OLTP and Data Warehouse Architecture of Data Warehouse OLAP its Types OLAP MOLAP HOLAP ODS (Operational Data Store) Star Schema Snowflake Schema Fact Table Granularity or Grain Dimension Table Degenerate Dimension Junk Dimension Conformed Dimension Role Playing Dimension Fast Changing Dimension Slowly Changing Dimension SCD Type 1 SCD Type [...]

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A dimensions is said to fast changing or rapidly changing dimensions if one or more of its attributes changes very fast and in many rows. e.g. Consider a Employee dimensions where there are 1000 rows in it. On an average each employee changes its 10 attribute in a year. Now if use type 2 approach [...]

Understanding OLAP and Type of OLAP


Online analytical processing is the capability to store and manage data in such a way the it can be used to generate actionable information which can be useful in decision making. As per BI architecture OLAP sits between Data Warehouse and Data Access tools. OLAP is useful in Transforming data into multidimensional cubes. Store pre-aggregated [...]


Same dimension which plays different role to the fact is called as role playing dimension. Its generally implemented using views in dimensional modeling. e.g. Suppose there are two date entities in employeehistory_fact fact table one is hire_date and another is release_date. Now to handle this situation instead of creating two separate dimension table we can [...]

Data Warehousing Architecture & Components


Since we know what is data warehouse and its benefits its time to dig deeper to understand typical architecture of data warehouse and its architecture. Following diagram depicts different components of Data Warehouse architecture. Operational Source System Its the traditional OLTP systems which stores transaction data of the organizations business. Its generally used one record [...]