What is Data Warehouse (Data Warehouse)-Alibaba Cloud Developer Community

Data Warehouse (Data Warehouse) is a theme-Oriented (Subject Oriented), integrated (Integrate), relatively stable (Non-Volatile), and Time Variant-Oriented Data set, used to support management decisions. We can understand the concept of data warehouse from two levels. First, data warehouse is used to support decision-making and is oriented to analytical data processing. It is different from the existing operational database of enterprises. Second, A data warehouse is an effective integration of multiple heterogeneous data sources. After integration, it is reorganized according to the topic and contains historical data. The data stored in the data warehouse is generally not modified.

According to the definition of data warehouse, data warehouse has the following four features:

1. Theme-oriented. The data organization of an operational database is oriented to transaction processing tasks. Each business system is separated from each other, and the data in the data warehouse is organized according to a certain subject domain. Topic is an abstract concept, which refers to the key aspects that users pay attention to when using data warehouses to make decisions. A topic is usually related to multiple operational information systems.

2. Integrated. Transaction processing-oriented operational databases are usually related to specific applications. Databases are independent of each other and are often heterogeneous. The data in the data warehouse is obtained through systematic processing, aggregation and collation on the basis of extracting and cleaning the original scattered database data. The inconsistency in the source data must be eliminated, to ensure that the information in the data warehouse is consistent global information about the entire enterprise.

3. Relatively stable. Data in an operational database is usually updated in real time and changes as needed. The data in the data warehouse is mainly used for decision-making and analysis of enterprises. The data operations involved are mainly Data Query. Once a data enters the data warehouse, it is generally retained for a long time, in other words, data warehouses generally have a large number of query operations, but few modification and deletion operations are required. Generally, only regular loading and refreshing are required.

4. Reflect historical changes. Operational databases mainly focus on data in a certain period of time. Data in a data warehouse usually contains historical information. The system records the time when an enterprise starts to apply data warehouse. The information of each stage up to now, through which quantitative analysis and prediction can be made on the development process and future trend of the enterprise.

The construction of enterprise data warehouse is based on the accumulation of existing enterprise business systems and a large amount of business data. Data warehouse is not a static concept. Only by handing over information to users who need it in time for them to make decisions to improve their business operations can Information play a role and make sense. The fundamental task of Data Warehouse is to sort out, summarize and reorganize the information and provide it to the corresponding management decision-making personnel in time. Therefore, from the perspective of industry, data warehouse construction is a project and a process.

The entire data warehouse system is a four-level architecture, as shown in the following figure.

Architecture of data warehouse system

In the mid-1980s, the father of data warehouse William H. Mr. Inmon defined the concept of data warehouse in his book "building data warehouse", and then gave a more accurate definition: Data warehouse is subject-oriented in enterprise management and decision-making, an integrated, time-related, and non-modifiable data set. Unlike other database applications, data warehouse is more like a process that integrates, processes, and analyzes business data distributed throughout the enterprise. Rather than a product that can be purchased.

This article is forwarded from loose_went blog, original link: http://www.cnblogs.com/michaelxu/archive/2009/03/12/1409299.html , if you need to reprint, please contact the original author.

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