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Schemas in Data Warehouse

Schema in Data Warehouse The term schema means logical description of the entire database. It is a collection of database objects such as tables, views, sequences, synonyms and indexes. It includes the name, description of data types such as data items and aggregates. Database uses RDBMS on the other hand data warehouse uses schema such as star, snowflake and fact constellation. Star Schema It is the simplest data warehouse schema. It looks like a star with points radiating from a center that’s why it is called star schema. In star schema there are one fact table and multiple dimension tables containing a bulk of data with redundancy. It can be simple or complex, simple star schemas contain one fact table and complex contains multiple fact tables. Fact Table The fact table represents attributes such as time, products and suppliers. It has two types of columns-foreign key to dimension tables...

Data Warehouse definition & its advantages

  Introduction A data warehouse is a central repository to store current and historical data for generating reports such as annual and quarterly comparisons that help for senior management for making good decision. In other words data warehouse is a repository of subjectively selected & suitable operational data, which can successfully answer any adhoc, complex, statistical or analytical queries. Data comes from various online transaction processing (OLTP) and other sources such as selected extracted and organized data in the data warehouse which is used by online analytical application (OLAP) and user queries. Definition of data warehouse: A data warehouse is a subject-oriented, integrated, time-variant and non-volatile collection of data in support of management’s decision making process. SUBJECT-ORIENTED Data Warehouses are organized around major subject such as customer, supplier, product and sales. Data are organized according to subject instead of apart. Each type of...