What is the so-called relationship in a relational database management system?

What is the so-called relationship in a relational database management system?

The so-called relationship in the relational database management system means that the data model is a two-dimensional table format that meets certain conditions.

It has the advantages of an object-oriented database management system: it is easy to express various complex relationships between objects, and the association between methods and data is realized in the database through object encapsulation. #Icon identification, object polymorphism and night coverage are all supported.

Compared with the object database management system, it has relatively high performance, and can use the mature technology and research results of the relational database management system; for the relational database management system, it can better Meet application requirements.

Definition and manipulation of classes. Object-oriented database languages ​​can manipulate classes, including defining, generating, accessing, modifying, and canceling classes. The definition of a class includes defining the attributes, operation

characteristics, inheritance and constraints of the class, etc.

Extended information

Representative data management systems include: Oracle, Microsoft SQL Server, Access, MySQL and PostgreSQL, etc. . Usually database administrators will use a database management system to create a database system. The database management system not only has user-oriented functions, but also has system-oriented functions.

Due to the lack of unified standards, DBMS's performance, functions and many other aspects vary from system to system. Generally speaking, large systems have more comprehensive functions and are more powerful, while small systems have weaker functions.

The performance of the same type of system is also different. Generally, the main functions of a DBMS include:

Database definition function. DBMS provides corresponding data definition language to define the database structure. They are the framework for describing the database and are stored in the data dictionary. The data dictionary is the basic basis for

DBMS to access and manage data.

Data access function. DBMS provides a data manipulation language to implement basic access operations on database data: retrieval, insertion, modification and deletion.

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