What does database independence mean?

What does database independence mean?

Data independence is one of the most important goals of a database system, which enables data to be independent of applications. It can be said that the history of data processing is the history of the continuous evolution of data independence. In the manual management stage, data and programs are completely intertwined, and there is no independence at all. Any changes to the data structure require corresponding modifications to the application program;

After the emergence of the file system, although the two are separated , but in fact, the application program still needs to reflect the physical details such as the organization method and access method of the files on the storage device. Therefore, as long as any modification is made to the data, the program still needs to be modified. An important goal of the database system is to truly separate programs and data so that they can develop independently.

Data independence includes the physical independence of data and the logical independence of data.

Physical independence means that the user's application and the data in the database stored on the disk are independent of each other. That is, how the data is stored on the disk is managed by DBMS (DataBase Management System). The user program does not need to understand. What the application program has to deal with is only the logical structure of the data. In this way, when the physical storage of the data changes, the application program does not need to change. .

Logical independence means that the user's application program and the logical structure of the database are independent of each other, that is, when the logical structure of the data changes, the user program can also remain unchanged.

The independence of data and program separates the definition of data from the program, and the DBMS is responsible for data access, thus simplifying the preparation of application programs and greatly reducing the maintenance and modification of application programs. .

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