Full Name :Mohit saini
College Name : doon business school
Department :computer application
Semester :I
Subject Code :105
Subject Name :data mining
Study Material Description :notes
A data warehouse is a collection of data marts representing historical data from different operations in the company. This data is stored in a structure optimized for querying and data analysis as a data warehouse. Table design, dimensions and organization should be consistent throughout a data warehouse so that reports or queries across the data warehouse are consistent. A data warehouse can also be viewed as a database for historical data from different functions within a company.
The term Data Warehouse was coined by Bill Inmon in 1990, which he defined in the following way: "A warehouse is a subject-oriented, integrated, time-variant and non-volatile collection of data in support of management's decision making process". He defined the terms in the sentence as follows:
Subject Oriented: Data that gives information about a particular subject instead of about a company's ongoing operations.
Integrated: Data that is gathered into the data warehouse from a variety of sources and merged into a coherent whole.
Time-variant: All data in the data warehouse is identified with a particular time period.
Non-volatile: Data is stable in a data warehouse. More data is added but data is never removed.
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