#The development process of data management is divided into three stages. (Recommended learning: MySQL video tutorial)
Manual management stage
The data is not saved in the computer.
There is no special software to manage data
There is only the concept of program and no concept of file
Data is oriented to program
Because at this stage, the computer It is mainly used for calculation and does not store data. The important reason is that there is no storage device and the software engineering is not mature. Data and programs are not independent of each other, that is, a set of data corresponds to a program.
File system stage
Data can be saved on disk for a long time.
The logical structure of the data is different from the physical structure
The file organization is diversified
The data no longer belongs to a specific program and can be reused.
With the development of technology, storage devices have appeared. And software engineering has also developed, and the file system that emerged is specifically used to manage data in external storage. The emergence of the file system means to separate the data so that the data does not depend on a specific program.
However, when the amount of data continues to expand, the file system reveals three flaws
1. Data redundancy: Because each application corresponds to a file, because these files Without connection, it is possible for the same data to be stored repeatedly in multiple files.
2. Data inconsistency: This is a problem caused by data redundancy. When performing a data update operation, modifying the data of one file may cause the data of another file to be inconsistent.
3. Weak data connection: caused by the lack of connection between files. In order to solve the problems that arise in the file system, the data can be managed more advanced and effectively. Data management systems emerged, which is also the database technology we are familiar with.
Database stage
Use data model to represent complex data structure
Have high data independence
The database system is Provide users with a convenient user interface
The database system provides four aspects of data control functions
Database recovery
Database concurrency control
Data Integrity
Data security
In the database stage, we separate the application and data from each other, when the database provides a unified application interface. When the application changes, there is no need to care about the database; when the database changes, there is no need to consider the application. And the database also provides many features to prevent application misoperations from causing data loss, damage and other problems.
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