Common ProblemWhat does a database mean when it comes to the correctness and compatibility of data?What does a database mean when it comes to the correctness and compatibility of data?
The "integrity" of the database refers to the correctness and compatibility of the data. Integrity refers to the logical consistency, correctness, validity and compatibility of data in the database. The importance of integrity to the database system: 1. Database integrity constraints can prevent legitimate users from adding unsemantic data to the database when using the database; 2. Reasonable database integrity design can take into account both the integrity of the database and the security of the system. Efficiency; 3. Perfect database integrity helps to detect application software errors as early as possible.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
Database Integrity refers to the logical consistency, correctness, validity and compatibility of data in the database.
Database integrity is guaranteed by various integrity constraints, so it can be said that database integrity design is the design of database integrity constraints. Database integrity constraints can be implemented through DBMS or applications, and DBMS-based integrity constraints are stored in the database as part of the schema. The database integrity achieved through DBMS is designed according to the database design steps, while the database integrity achieved by application software is incorporated into the application software design.
Database integrity is very critical to the database application system, and its role is mainly reflected in the following aspects:
1. Database integrity constraints can prevent legitimate users from adding semantically inconsistent data to the database when using the database.
2. Using the integrity control mechanism based on DBMS to implement business rules is easy to define and understand, and can reduce the complexity of the application and improve the operating efficiency of the application. At the same time, the integrity control mechanism based on DBMS is centrally managed, so it is easier to achieve database integrity than applications.
3． Reasonable database integrity design can take into account both database integrity and system performance. For example, when loading a large amount of data, as long as the database integrity constraints based on the DBMS are temporarily invalidated before loading and then taken into effect, the integrity of the database can be guaranteed without affecting the efficiency of data loading.
4． In the functional testing of application software, perfect database integrity helps to detect application software errors as early as possible.
Database integrity constraints can be divided into six categories: column-level static constraints, tuple-level static constraints, relationship-level static constraints, column-level dynamic constraints, tuple-level dynamic constraints, and relationship-level dynamic constraints. Dynamic constraints are usually implemented by application software. The database integrity supported by different DBMS is basically the same.
When implementing database integrity design, there are some basic principles that need to be grasped:
1. Determine the system level and method of implementation based on the type of database integrity constraints, and consider the impact on system performance in advance. In general, static constraints should be included in the database schema as much as possible, while dynamic constraints are implemented by the application.
2. Entity integrity constraints and referential integrity constraints are the most important integrity constraints of relational databases, and they should be applied as much as possible without affecting the key performance of the system. It is worth spending a certain amount of time and space in exchange for the ease of use of the system.
3． On the other hand, multi-level triggering of triggers is difficult to control and errors are prone to occur. When it is absolutely necessary, it is best to use Before statement-level triggers.
4． During the requirements analysis stage, a naming convention for integrity constraints must be formulated, and try to use meaningful combinations of English words, abbreviations, table names, column names, and underscores to make them easy to identify and remember, such as: CKC_EMP_REAL_INCOME_EMPLOYEE, PK_EMPLOYEE, CKT_EMPLOYEE. If you use the CASE tool, there are generally default rules, which can be modified and used on this basis.
5. Database integrity must be carefully tested according to business rules to eliminate conflicts between implicit integrity constraints and the impact on performance as early as possible.
6． There must be a dedicated database design team responsible for the analysis, design, testing, implementation and early maintenance of the database from beginning to end. Database designers are not only responsible for the design and implementation of database integrity constraints based on DBMS, but also responsible for reviewing the database integrity constraints implemented by application software.
7． Appropriate CASE tools should be used to reduce the workload at each stage of database design. A good CASE tool can support the entire database life cycle, which will greatly improve the work efficiency of database designers and make it easier to communicate with users.
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