What is a data warehouse?

According to Bill Inmon (Considered the father of DW),

“A data warehouse is a subject-oriented, integrated, time-varying, non-volatile collection of data in support of the management’s decision-making process.”

According to Tom Wailgum (IT Journalist),

Optimistic miners who dropped everything to go west during the gold rush were looking for those sparkling little nuggets that promised to make them rich. In many respects, using a data warehouse is a lot like those journeys west. Companies that go about it the right way discover software packages that help them pickax their way through mountains of data. If they successfully implement data warehouses, they may uncover unexpected buying patterns to aid decision making, cut costs and improve customer service.

According to Stanford University,

“A Data Warehouse is a repository of integrated information, available for queries and analysis. Data and information are extracted from heterogeneous sources as they are generated….This makes it much easier and more efficient to run queries over data that originally came from different sources.”

According to US industry group Data Into Action,

Have you ever reviewed a report, put it down, and realized that as a result of your inspection you had more questions? How tough was it to get answers to the follow up questions? If you’re like most folks in business today the answer to the first question was an emphatic YES. To the second question, your answer might depend on whether or not you have an effective Data Warehouse in place.

For many, the answers to questions generated by the review of a production or ad-hoc report are not available for days or even weeks. Sometimes, we forget the question by the time we get the answer. A Data Warehouse, properly designed and implemented, should provide you with the ability to transform data into action. In this way, a decision-maker must have the ability to keep asking questions of their data until they have enough information to take action.

According to Ralph Kimball (Probably most well known person in Data Warehousing!)

“A copy of transaction data specifically structured for query and analysis”.

From Kimball’s book, “The Data Warehouse Toolkit”, Page 310.

 According to Colin Saunders (Data Warehouse Consultant),

“A repository of information that answers two questions,¬† ‘What does the world look like today?’ and ‘What did the world look like yesterday, last week, last month or last year, etc’ “.