At present, there is no unified definition in the data warehouse. The famous data warehouse expert Whinmon gives the following description in its book "Building The Data Warehouse": Data Warehouse is a topic (Subject Oriented) ), Integrated, relatively stable non-Volatile, reflects the data collection of Time Variant, is used to support management decisions. For the concept of data warehouse we can understand from two hieraries, first, data warehouses are used to support decisions, facing analytical data processing, which is different from an existing operating database; second, data warehouses are multiple heterogeneous The data source is effectively integrated, and the integration is recombined according to the subject, and the history data is stored, and the data stored in the data warehouse is generally no longer modified. According to the meaning of the data warehouse concept, the data warehouse has the following four features: 1, the topic. The data organization of the operating database is transaction to transaction tasks, and each of the business systems are separated, and data in the data warehouse is organized in accordance with a certain subject domain. The theme is an abstract concept that refers to the key aspects of the user who cares about the decision of the data warehouse, and one topic is typically associated with multiple operating information systems. 2, integrated. Transaction-oriented operational databases are typically associated with certain applications, and databases are independent of each other and are often heterogeneous. The data in the data warehouse is based on system processing, summary, and organized by system processing, summary, and organized, and must eliminate inconsistency in the source data, to ensure that the information within the data warehouse is about the entire The consistent global information of the company. 3, relatively stable. Data in the operating database usually updates in real time, and the data changes in time as needed. The data warehouse data is mainly used for enterprise decision analysis. The data operation involved is mainly data queries. Once a data enters the data warehouse, it will be reserved for a long time, that is, a large number of query operations in the data warehouse. However, modifications and deletions are rare, usually only regular loading, refresh. 4, reflect the changes in history. The operational database is mainly concerned about the data in a time period, and the data in the data warehouse usually contains historical information. The system records that companies from the past time (such as starting application data warehouses) to the current stages. Information, through this information, quantitative analysis and prediction can be quantitatively analyzed and future trends. The construction of corporate data warehouse is based on the accumulation of existing enterprise business systems and large number of business data. The data warehouse is not a static concept, and only the information is given to the user who needs this information. For them to improve their business operations, the information can play a role, and the information is meaningful. The information is intended to summarize and reorganize, and the corresponding management decision makers will be provided to the corresponding management decision makers. It is the fundamental task of the data warehouse. Therefore, from the perspective of the industry, the construction of data warehouses is a project and is a process. The entire data warehouse system is an architecture containing four hierarchies, which is specifically represented by the following figure.
Data warehouse system architecture
