Hierarchical database presents data according to hierarchical structure (tree structure); Grid database is a database based on grid data model by using grid principles and methods. Relational database refers to a database that uses relational models to organize data.
The role of database
1. Realize data sharing: Data sharing includes that all users can access the data in the database at the same time, and users can use the database in various ways through the interface and provide data sharing.
2. Reduce data redundancy: Compared with the file system, because the database realizes data sharing, users are prevented from creating application files independently. Reduce a large number of duplicate data, reduce data redundancy and maintain data consistency.
3. Maintain data independence: data independence includes logical independence (the logical structure of database and application is independent of each other) and physical independence (the change of physical structure of data does not affect the logical structure of data).
4. Centralized control of data: In the file management mode, the data is in a decentralized state, and different users or the same user do nothing with their own files in different processes. Database can be used to centrally control and manage data, and data model can be used to express the organization of various data and the relationship between data.