Concept of Relational Database

1. Concepts of relational databases

A relational database refers to a database that uses a relational model to organize data. The relational model was developed by IBM researcher E. f. dr. codd first proposed that the concept of relational model had been fully developed and gradually become the mainstream model of database architecture in the next few decades. In short, a relational model refers to a two-dimensional table model, and a relational database is a data organization composed of two-dimensional tables and their relationships. Common concepts in the relational model are listed below.

Link: it can be understood as a two-dimensional table. Each link has a relational name, that is, the table name.

Tuples: a row in the orders table, which is often called a record in the database.

Attribute: it can be understood as a column in the tables Table, which is often called a field in the database.

Field: The value range of the attribute, that is, the value limit of a column in the database.

Keywords: A group of attributes that can uniquely identify tuples. A database is often called a primary key and consists of one or more columns.

Link mode: describes a link. The format is: Link name (attribute 1, attribute 2 ,..., Attribute N ). A database is usually called a table structure.

2. Advantages of relational databases

Compared with databases of other models, relational databases have the following advantages:

Easy to understand: the structure of a two-dimensional table is very close to the logic world. The relational model is easier to understand than other models such as mesh and hierarchy.

Easy to use: the general SQL language makes it very convenient to operate relational databases. programmers and even data administrators can operate databases logically without having to understand the underlying implementation.

Easy to maintain: Rich integrity (entity integrity, reference integrity, and user-defined integrity) greatly reduces the probability of data redundancy and data inconsistency.

In recent years, non-relational databases have developed rapidly in theory, such as the mesh model, object model, and semi-structured model. The mesh model has high performance advantages and is usually used in systems with high performance requirements. The object model conforms to the idea of object-oriented applications and can be perfectly connected with programs, there is no need for other intermediate conversion components, such as many O \ r mapping components. The semi-structured model is developed with the development of XML, now we have a lot of semi-structured database models. However, with its maturity in theory, ease of use, and extensive application, relational databases are still the mainstream solutions in system applications.

Answer

Relational databases support relational models. In short, relational models refer to the relational table model. Compared with other models, relational databases have the advantages of easier understanding, easier use, and simpler maintenance.