Database system is a kind of management data system, first design to the data, the data will be from the data managementHistoryLook at the development of the database system. After we reached the database stage, we began to discuss our course. First look at the application section: 1, analyze the data Design the use of the database, first of all to the problemAnalysis。 So the problem in the database world does not revolve around the data! So start by analyzing the data first.data analysis, because people often can not solve the problem of one step. So people's analysis of the database is generally from the macro to the micro, the use of abstract methods to gradually refine the analysis of data. In the process of data abstraction, people get four kinds of models in different stages of data abstraction.
as people get four kinds of models through continuous refinement, these models also naturally form a hierarchical relationship . This hierarchical relationship solves different levels of problems, and the levels are linked by mapping. This kind of database structure analysis is good after the hands-on design.
2. Design Databaseto design a database, first plan the whole, and then figure out the requirements. With a clearer demand, the following are specific designs for each model.
in the conceptual model design, a more important tool is the e-r diagram , through the E-r diagram can be more intuitive to understand the system will be developed. If a good system is designed, then it is natural to try its charms.
3. UseThe most basic use of the database is the SQL language, in particular, the SQL language is actually on the table to Delete and change . And the SQL language after the expansion of T-SQL is also added some process control. The use of database language after learning, you must learn to manage the database.
4. ManagementThe premise of using Database system is that the system can guarantee the correctness and security of the data, and ensure that the management of the database system can not be separated. The most direct data correctness is the use of constraints , limiting the range of data. The second is the transaction mechanism to ensure that the data will not be lost unexpectedly as the system runs. In parallel with multiple transactions in the system, parallel control of the system is necessary. At the end of the worst case, it is guaranteed to be restored to its original state.
Ensure that the correctness of the data still does not meet people's needs, because the operation of the data is privileged, just as we use the access control in the program to restrict the operation of the data. We want to manage the security of the data
To prevent the damage to the system from illegal operation and accidental failure. See the theory section again:application always have the corresponding theory to support and guidance, here we follow the order from the theory of the table to learn, in the table design always have a good or bad standard bar, blindly build a table will cause a lot of trouble, this put forward the paradigm . Building a table with a unified standard, the next is to use the table is the Operation table, the table has a lot of operations, you can not tell why this is not always possible. So here's a look at the theory of these operations for table Operations .
Aerial view Database System principle
