What are the four components of a relational database?
The relational model is the foundation of any relational database management system (RDBMS). A relational model has two core components: a collection of objects or relationships, operations that act on the objects or relationships, and data integrity rules. In other words, a relational database has a place to store data, a way to create and retrieve data, and a way to confirm the logical consistency of the data.
What are the five parts of a relational database system
What are the parts of a database system? A database system DBS (DataBaseSystem, or DBS for short) usually consists of software, a database, and a data manager. Its software mainly includes operating systems, various host languages, utility programs and database management systems. The database is managed by the database management system, and the insertion, modification and retrieval of data are carried out through the database management system. The data administrator is responsible for creating, monitoring, and maintaining the entire database so that the data can be used effectively by anyone who is authorized to use it. The database administrator is usually a person with a high level of business and seniority.
The database system generally consists of four parts:
(1) Database (database, DB) is a collection of data stored in a computer for a long period of time, which is organized and can be shared. The data in the database according to a certain mathematical model organization, description and storage, has a small redundancy, high data independence and scalability, and can be shared for a variety of users.
(2) hardware: a variety of physical equipment that constitutes a computer system, including the external equipment required for storage. Hardware configuration should meet the needs of the entire database system.
(3) software: including operating systems, database management systems and applications. Database management system (databasemanagementsystem, DBMS) is the core software of the database system, is working under the support of the operating system, to solve how to scientifically organize and store data, how to efficiently obtain and maintain data system software. Its main functions include: data definition function, data manipulation function, database operation management and database establishment and maintenance.
(4) Personnel: there are four main categories. The first category is system analysts and database designers: system analysts are responsible for the application system requirements analysis and specification of the description, they work with users and database administrators to determine the hardware configuration of the system, and participate in the outline design of the database system. Database designers are responsible for the identification of data in the database and the design of the schema at all levels of the database. The second group, application programmers, are responsible for writing applications that use the database. These applications retrieve, create, delete, or modify data. The third category is the end users who access the database using the system’s interface or query language. The fourth category of users is the databaseadministrator (DBA), who is responsible for the overall information control of the database.The specific responsibilities of the DBA include: specifying the content and structure of the information in the database, deciding on the database’s storage structure and access strategy, defining the database’s security requirements and integrity constraints, monitoring the database’s use and operation, and being responsible for performance improvement of the database, reorganization and refactoring of the database to improve the performance of the system.
Where application programs are included in the scope of software, they are database applications such as development tools, talent management systems, and information management systems.
The basic data structure of the relational data model is
The basic data structure of the relational data model is the following:
Relational databases, are databases that have adopted the relational model for organizing data, which store data in the form of rows and columns to make it easier for the user to understand.Relational databasesThis series of rows and columns is known as a table, and a set of tables make up a database.
Users retrieve data from a database through a query, which is an execution code used to qualify certain areas of the database. The relational model can be simply understood as a two-dimensional table model, and a relational database is a data organization consisting of two-dimensional tables and the relationships between them.
In a relational database, the basic data structure is a two-dimensional table, and the links between tables are represented by public fields in different tables. Each relational model is not isolated, they are not randomly stacked together in a pile of two-dimensional tables, to correctly reflect things and the links between things, the need for careful relational database design.
1. Storage: the traditional relational database using the table storage, data is stored in rows and columns, to read and query are very convenient.
2. Storage structure: relational databases store data in accordance with the structured approach, each data table must be defined for each field (that is, the first definition of the structure of the table), and then deposited into the data according to the structure of the table.
The advantage of this is that the form and content of the data has been defined before the data is deposited, so the reliability and stability of the entire data table are higher, but the problem is that once the data is deposited, if you need to modify the structure of the data table will be very difficult.
3. Storage specification: relational databases in order to avoid duplication, standardization of data and make full use of the storage space, the data in accordance with the form of the smallest relational table for storage, so that data management can become very clear, at a glance, of course, this is mainly a data table.
If it is a multi-table situation is not the same, because the data involves a number of data tables, there is a complex relationship between the data tables, with the increase in the number of data tables, data management will become more and more complex.
4. Expansion: As the relational database will be stored in the data table, the bottleneck of the data operation appears in the operation of multiple data tables, and the more data tables the more serious the problem, if you want to alleviate this problem, you can only improve the processing power, that is, to choose the faster performance of higher performance computers.
This approach can be certain expansion space, but this expansion space must be very limited, that is, relational databases only have the ability to expand vertically.
5. Query: relational databases use Structured Query Language (SQL) to query the database, SQL has long been supported by various database vendors, and has become the standard in the database industry.
It can support database CRUD (add, query, update, delete) operations, with very powerful features, SQL can be used similar to the index method to speed up the query operation.