Data Management Concept: A series of activities of data processing, data collection, finishing, storage, maintenance, retrieval, transmission, etc., as basic operations, the basic operation link, called the development of data management data management 1. Artificial management stage features: a. The data is not saved in the machine B. No software system manages C. Only program concept, no file concept d. A set of data corresponds to a program, and the data is an application 2. File system phase features: a. The data is saved on an external exotic disk in the form of a file. The physical structure of the data is different from the logical structure (the program does not have to care about the physical location of the data) C. Differentiated D. Data no longer belongs to a particular application, you can reuse the disadvantages: A. Data redundancy is large: for application, unable to share B. Data of the data of C. The data is weak (the file is independent, lack of contact) 3. Database phase guidance ideas: implement unified, centralized, independent management to all data, so that the data is stored independent of the data of the data, and implements data sharing. Features: 1. The data structure 2 is indicated by a complex data model. Data independence a) Physical independence, logic independence B) has high data and procedures independence, data description, definition from the application, existence independent of the application, independent, and independent of each other. 3. With a good user interface, users can easily develop and use databases 4. Unified Data Control Function a) Sharing is generally concurrent, multiple users use the database at the same time, and should provide the following functions: i. Data security control II. Data Integrity Control (Positiveness, Validity, Compatibility) III. Concurrent Control IV. Data Recovery 5. The operation of the data is not necessarily recorded, and the system's flexibility can be added in units of data items. (TIP: File system The operation of the data is recorded as units) 6. Data Sharing a) Sharing is a multi-user, a variety of applications, and multiple languages to share data sets. b) Data sharing of file level, record stage, and data item level can be implemented. 7. Controllable Data Redundancy A) Data does not have to repeat storage, save storage space, guarantee data consistency B) Theoretically can do a redundant degree 0 c) can be intentionally arranged for several redundancy, by user control, called Controllable redundant database concept: The database is a collection of relevant data for unified management, which can share and have minimal redundancy, close relationship between data, and high data independence. Summary: In the database phase, the database accounts for the center position of the application, and the data inventory is placed in various applications, and the data is maintained, and the database is a static concept, and it is reflected through the application database. Its value. Basic Concept: Data: Describe the symbol record database (Database DB): Long-term structured large amount of shared data collection in the computer. Database Management System (DBMS): A layer of data management software located between the user and the operating system. Database System (DBS): The system constitutes the system after the database is introduced, which is generally composed of a database, database management system (and its development tool), application system, database administrator, and user.
