How to ensure the data Independence of the Database

This article will explain in detail how to ensure the data independence of the database. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

In order to ensure the independence of the logical data of the database, it is necessary to modify the images of the schema and the external schema, in which the schema describes the global logical structure of the data, and the external schema describes the local logical structure of the data; for each external schema, the database system has an external schema / schema image, which defines the corresponding relationship between the external schema and the schema.

To ensure the independence of the database logical data, what needs to be modified is the image of the schema and the external schema.

The schema describes the global logical structure of the data, while the external schema describes the local logical structure of the data.

There can be any number of external modes corresponding to the same pattern. For each external schema, the database system has an external schema / schema image, which defines the corresponding relationship between the external schema and the schema. These image definitions are usually included in the description of each pattern. When the schema changes, the database administrator can make corresponding changes to each external schema / schema image, which can keep the external schema unchanged. The application program is written according to the external mode of the data, so that the application program does not have to be modified, which ensures the logical independence of the data and the program.

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