How to delete data in the data table
Method: 1. Use the DELETE statement to delete one or more rows of data in the table. The syntax is "DELETE FROM table name [WHERE clause]"; if the "WHERE clause" is omitted, you can delete the data in the table. All data. 2. Use the "TRUNCATE TABLE table name;" statement to delete all data in the table.
The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.
MySQL provides the DELETE and TRUNCATE keywords to delete data in the table.
1. DELETE statement
The DELETE statement can delete one or more rows of data in the table. Syntax format:
DELETE FROM <表名> [WHERE 子句] [ORDER BY 子句] [LIMIT 子句]
The syntax description is as follows:
: Specify the name of the table to delete data.
ORDER BY clause: Optional. Indicates that when deleting, rows in the table will be deleted in the order specified in the clause.
WHERE clause: Optional. Indicates that the deletion conditions are limited for the deletion operation. If this clause is omitted, it means that all rows in the table are deleted.
LIMIT clause: Optional. Used to tell the server the maximum number of rows to be deleted before the control command is returned to the client.
Note: When the WHERE condition is not used, all data will be deleted.
Example: Delete all data in the table
mysql> DELETE FROM tb_courses_new; Query OK, 3 rows affected (0.12 sec) mysql> SELECT * FROM tb_courses_new; Empty set (0.00 sec)
Copy after login2. TRUNCATE statement
The TRUNCATE keyword is used to completely clear a table. The syntax format is as follows:
TRUNCATE [TABLE] 表名
Copy after loginThe TABLE keyword can be omitted.
Example: Delete all data in the table
mysql> TRUNCATE TABLE tb_student_course; Query OK, 0 rows affected (0.04 sec) mysql> SELECT * FROM tb_student_course; Empty set (0.00 sec)
Copy after login(Recommended tutorial: mysql video tutorial)
The difference between TRUNCATE and DELETE
Logically speaking, the TRUNCATE statement has the same effect as the DELETE statement, but in some cases, there are differences in their use.
DELETE is a DML type statement; TRUNCATE is a DDL type statement. They are both used to clear the data in the table.
DELETE deletes records row by row; TRUNCATE directly deletes the original table and then creates an identical new table instead of deleting the data in the table row by row. Execute data faster than DELETE. Therefore, when you need to delete all data rows in the table, try to use the TRUNCATE statement to shorten the execution time.
DELETE After deleting data, the data can be retrieved with event rollback; TRUNCATE does not support transaction rollback, and data cannot be retrieved after deletion.
DELETE After deleting data, the system will not reset the counter of the auto-increment field; after TRUNCATE clears the table records, the system will reset the counter of the auto-increment field.
DELETE has a wider scope of use because it can delete part of the data by specifying conditions through the WHERE clause; TRUNCATE does not support the WHERE clause and can only delete the entire data.
DELETE will return the number of rows with deleted data, but TRUNCATE will only return 0, which is meaningless.
For more programming-related knowledge, please visit: Programming Video! !
The above is the detailed content of How to delete data in the data table. 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
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Assassin's Creed Shadows: Seashell Riddle Solution3 weeks ago By DDDWhat's New in Windows 11 KB5054979 & How to Fix Update Issues2 weeks ago By DDDWhere to find the Crane Control Keycard in Atomfall3 weeks ago By DDDAssassin's Creed Shadows - How To Find The Blacksmith And Unlock Weapon And Armour Customisation1 months ago By DDDRoblox: Dead Rails - How To Complete Every Challenge3 weeks ago By DDD
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
CakePHP Tutorial
1387
52
See all articles
How to open phpmyadmin
Apr 10, 2025 pm 10:51 PM
You can open phpMyAdmin through the following steps: 1. Log in to the website control panel; 2. Find and click the phpMyAdmin icon; 3. Enter MySQL credentials; 4. Click "Login".
MySQL: An Introduction to the World's Most Popular Database
Apr 12, 2025 am 12:18 AM
MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.
How to use single threaded redis
Apr 10, 2025 pm 07:12 PM
Redis uses a single threaded architecture to provide high performance, simplicity, and consistency. It utilizes I/O multiplexing, event loops, non-blocking I/O, and shared memory to improve concurrency, but with limitations of concurrency limitations, single point of failure, and unsuitable for write-intensive workloads.
MySQL's Place: Databases and Programming
Apr 13, 2025 am 12:18 AM
MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen
Why Use MySQL? Benefits and Advantages
Apr 12, 2025 am 12:17 AM
MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.
Monitor Redis Droplet with Redis Exporter Service
Apr 10, 2025 pm 01:36 PM
Effective monitoring of Redis databases is critical to maintaining optimal performance, identifying potential bottlenecks, and ensuring overall system reliability. Redis Exporter Service is a powerful utility designed to monitor Redis databases using Prometheus. This tutorial will guide you through the complete setup and configuration of Redis Exporter Service, ensuring you seamlessly build monitoring solutions. By studying this tutorial, you will achieve fully operational monitoring settings
How to view sql database error
Apr 10, 2025 pm 12:09 PM
The methods for viewing SQL database errors are: 1. View error messages directly; 2. Use SHOW ERRORS and SHOW WARNINGS commands; 3. Access the error log; 4. Use error codes to find the cause of the error; 5. Check the database connection and query syntax; 6. Use debugging tools.
How to connect to the database of apache
Apr 13, 2025 pm 01:03 PM
Apache connects to a database requires the following steps: Install the database driver. Configure the web.xml file to create a connection pool. Create a JDBC data source and specify the connection settings. Use the JDBC API to access the database from Java code, including getting connections, creating statements, binding parameters, executing queries or updates, and processing results.
