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This article will explain in detail what language sql refers to. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Structured query language (Structured Query Language) referred to as SQL, is a special purpose programming language, is a database query and programming language, used to access data and query, update and manage relational database systems.

Structured query language is a high-level non-procedural programming language that allows users to work on high-level data structures. It does not require the user to specify the data storage method, nor does it require the user to know the specific data storage method, so different database systems with completely different underlying structures can use the same structured query language as the interface for data input and management. Structured query language statements can be nested, which makes it have great flexibility and powerful functions.

The SQL language was proposed by Boyce and Chamberlin in 1974 and was first implemented on the relational database system SystemR developed by IBM Company. Because of its outstanding advantages such as rich functions, convenient and flexible use, concise and easy to learn language, it is deeply welcomed by the computer industry and computer users. In October 1980, X3H2, the database committee of the American National Standards Institute (ANSI), approved SQL as the American standard for relational database language, and published the standard SQL in the same year. Shortly after that, the International Organization for Standardization (ISO) made the same decision.

Functionally, SQL can be divided into three parts: data definition, data manipulation and data control.

The core part of SQL is equivalent to relational algebra, but it has many characteristics that relational algebra does not have, such as aggregation, database update and so on. It is a comprehensive, universal and highly functional relational database language. Its characteristics are as follows:

1. Data description, manipulation, control and other functions are integrated.

2. Two ways of use and unified grammatical structure. SQL can be used in two ways. One is online interactive use, in which SQL is actually used as a self-contained language. Another way is to embed it into a high-level programming language (such as C, etc.). The former method is suitable for non-computer professionals, and the latter is suitable for computer professionals. Although it is not used in the right way, the grammatical structure of the language is basically the same.

3. Highly non-procedural. SQL is a fourth generation language (4GL), users only need to put forward "what to do", do not need to specify "how to do", such as access path selection and specific processing operations are automatically completed by the system.

4. The language is concise and easy to learn and use. Although SQL is very powerful, the language is very concise, and only nine verbs are used in the core function. The grammar of SQL is close to spoken English, so it is easy for users to learn and use it.

Function

SQL has data definition, data manipulation and data control.

1. SQL data definition function: it can define the three-level schema structure of the database, namely, external schema, global schema and internal schema structure. In SQL, the outer schema is called View, and the global schema is called Schema. The inner schema is automatically implemented by the system according to the database schema, and generally does not need to be asked by the user.

2. SQL data manipulation function: including data insertion, deletion and modification of basic tables and views, especially with strong data query function.

3. The data control function of SQL: the main function is to control the access rights of users to ensure the security of the system.

Language features

SQL has a unified style

SQL can independently complete all the activities in the database life cycle, including defining relational schema, recruiting data, establishing database, query, updating, maintenance, database reconstruction, database security control, etc., which provides a good environment for database application system development. After the database is put into operation, the schema can be modified step by step at any time as needed, and does not affect the operation of the database. So that the system has good expandability.

Highly non-procedural

The data manipulation language of non-relational data model is a process-oriented language, and the access path must be specified when using it to complete user requests. When using SQL for data operation, users only need to propose "what to do" without indicating "how to do". Therefore, users do not need to know the access path, the choice of access path and the operation process of SQL statements are completed automatically by the system. This not only greatly reduces the burden on users, but also helps to improve data independence.

Set-oriented operation mode

SQL adopts set operation mode. Not only the search result can be a collection of tuples, but also the objects of an insert, delete and update operation can also be a collection of tuples.

Provide two ways of use in the same grammatical structure

SQL is both a self-contained language and a human-embedded language. As a self-contained language, it can be used independently for the use of online interaction, and users can directly input SQL commands on the terminal keyboard to operate the database. As an embedded language, SQL statements can be embedded into programs in high-level languages (such as C, C #, JAVA) for programmers to use when designing programs. In the two different ways of use, the grammatical structure of SQL is basically the same. This provides two different modes of operation with a unified grammatical structure, providing users with great flexibility and convenience.

The language is concise and easy to learn and use.

SQL is extremely powerful, but because of its ingenious design and concise language, only nine verbs are used to complete the core functions of data definition, data manipulation and data control: CREATE, ALTER, DROP, SELECT, INSERT, UPDATE, DELETE, GRANT, REVOKE. And SQL language grammar is simple, close to spoken English, so it is easy to learn and use.

This is the end of the article on "what language sql refers to". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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