What are the four categories of database languages?
Database languages are divided into four categories: 1. Data query language DQL; 2. Data manipulation language DML; 3. Data definition language DDL; 4. Data control language DCL.
The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.
SQL language is divided into four categories: data query language DQL, data manipulation language DML, data definition language DDL, and data control language DCL.
1. Data query language DQL
The basic structure of data query language DQL is a query block composed of SELECT clause, FROM clause, and WHERE
clause ：
SELECT <field name table>##FROM
WHERE
CREATE TABLE/VIEW/INDEX/SYN/CLUSTERTable view index synonym cluster
DDL operations are submitted implicitly! Cannot rollback4. Data control language DCLData control language DCL is used to grant or revoke certain privileges to access the database, and control the time and effect of database manipulation transactions, and perform operations on the database. Surveillance etc. Such as:1) GRANT: Authorization.
2) ROLLBACK [WORK] TO [SAVEPOINT]: Roll back to a certain point. Rollback---ROLLBACK The rollback command returns the database state to the last submitted state. The format is:SQL>ROLLBACK;
3) COMMIT [WORK]: Submit. There are three types of submitted dataIn the insertion, deletion and modification operations of the database, the transaction is completed only when it is submitted to the database. Before the transaction is committed, only the person operating the database has the right to see what has been done. Others can only see it after the final commit is completed. There are three types of submitted data: explicit submission, implicit submission and automatic submission. These three types are described below.(1) Explicit submission
The submission completed directly using the COMMIT command is an explicit submission. The format is:SQL>COMMIT;
(2) Implicit submissionThe submission completed indirectly using SQL commands is implicit. submission. These commands are:
ALTER, AUDIT, COMMENT, CONNECT, CREATE, DISCONNECT, DROP, EXIT, GRANT, NOAUDIT, QUIT, REVOKE, RENAME.(3) Automatic submission
(Recommended tutorial:若把AUTOCOMMIT设置为ON，则在插入、修改、删除语句执行后， 系统将自动进行提交，这就是自动提交。其格式为： SQL>SET AUTOCOMMIT ON；
Copy after loginmysql video tutorial)
The above is the detailed content of What are the four categories of database languages?. For more information, please follow other related articles on the PHP Chinese website!
Statement of this WebsiteThe content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌Hello Kitty Island Adventure: How To Get Giant Seeds1 months ago By 尊渡假赌尊渡假赌尊渡假赌How Long Does It Take To Beat Split Fiction?4 weeks ago By DDDR.E.P.O. Save File Location: Where Is It & How to Protect It?4 weeks ago By DDDTwo Point Museum: All Exhibits And Where To Find Them1 months ago By 尊渡假赌尊渡假赌尊渡假赌
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
deepseek web version official entrance
Mar 12, 2025 pm 01:42 PM
The domestic AI dark horse DeepSeek has risen strongly, shocking the global AI industry! This Chinese artificial intelligence company, which has only been established for a year and a half, has won wide praise from global users for its free and open source mockups, DeepSeek-V3 and DeepSeek-R1. DeepSeek-R1 is now fully launched, with performance comparable to the official version of OpenAIo1! You can experience its powerful functions on the web page, APP and API interface. Download method: Supports iOS and Android systems, users can download it through the app store; the web version has also been officially opened! DeepSeek web version official entrance: ht
In-depth search deepseek official website entrance
Mar 12, 2025 pm 01:33 PM
At the beginning of 2025, domestic AI "deepseek" made a stunning debut! This free and open source AI model has a performance comparable to the official version of OpenAI's o1, and has been fully launched on the web side, APP and API, supporting multi-terminal use of iOS, Android and web versions. In-depth search of deepseek official website and usage guide: official website address: https://www.deepseek.com/Using steps for web version: Click the link above to enter deepseek official website. Click the "Start Conversation" button on the homepage. For the first use, you need to log in with your mobile phone verification code. After logging in, you can enter the dialogue interface. deepseek is powerful, can write code, read file, and create code
How to solve the problem of busy servers for deepseek
Mar 12, 2025 pm 01:39 PM
DeepSeek: How to deal with the popular AI that is congested with servers? As a hot AI in 2025, DeepSeek is free and open source and has a performance comparable to the official version of OpenAIo1, which shows its popularity. However, high concurrency also brings the problem of server busyness. This article will analyze the reasons and provide coping strategies. DeepSeek web version entrance: https://www.deepseek.com/DeepSeek server busy reason: High concurrent access: DeepSeek's free and powerful features attract a large number of users to use at the same time, resulting in excessive server load. Cyber Attack: It is reported that DeepSeek has an impact on the US financial industry.
