A, Data Warehouse data warehouse
“A data warehouse is a subject-oriented, integrated, nonvolatile, and time-variant collection of data in support of management’s decisions.”——Bill Inmon（“Building the Data Warehouse”，1990）
Chinese Interpretation: A data warehouse is a subject-oriented, integrated, relatively stable, reflecting the historical changes in data collection to support management decisions. - Bill Grace door ( "data warehouse", 1990)
Two, Data Warehouse Data Model
Data model can be divided into physical model and logical model.
The relationship between logical data model representations of business-related data, a database-independent design, from the perspective of business enterprises and height set out subject area model (subject field model), and then gradually drill down to entities (entity), attributes (properties).
Physical Models and related database management system, is build on the system of data architecture, so the need to consider the data type (data type) design, performance space and related topics.
In order to output data model, usually after four stages of modeling, specific tasks and outputs phase may refer to another article "data modeling" Related articles:
Three, Entities entities
On the database, the entity often refers to the collection of certain things.
Four, Subject theme
Theme, is an abstract concept, correspondence analysis of a target company in the field of macroeconomic analysis involved.
Data in the data warehouse is a subject-oriented organized. Theme is determined according to the requirements analysis. This is in accordance with the requirements of the application or data processing to organize the data are different. For example, "Sales Analysis" is a field of analysis, data warehouse applications and therefore this topic is "Sales Analysis."
Fifth, the subject field
Subject field is usually associated more closely the topic of data collection. According to business concerns, these data themes into different subject areas. Determine the subject field must be jointly completed by the end user and the data warehouse designers.
June and subject area, topic, entity relationship
Theme design is further broken down to the subject field, refinement process. The following subject field may have multiple themes, the theme can also be divided into more sub-topic, and then the entity is indivisible minimum unit. , Topic, theme domain entity relationship as shown below:
