search
HomeDatabaseMysql TutorialHow to clear data table data in mysql

How to clear data table data in mysql

Feb 04, 2021 am 10:28 AM
mysqlClear data

In mysql, you can use the "DELETE" and "TRUNCATE" keywords to clear the data in the data table. The specific syntax is "DELETE FROM data table;" and "TRUNCATE TABLE data table;".

How to clear data table data in mysql

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.

MySQL DELETE keyword

In MySQL, you can use the DELETE statement to delete one or more rows of data in a table.

Use the DELETE statement to delete data from a single table. The syntax format is:

DELETE FROM <表名> [WHERE 子句] [ORDER BY 子句] [LIMIT 子句]

The syntax description is as follows:

  • ##: Specify the table name from which data is to be deleted.

  • 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.

    Delete all data in the table

    Example: Delete all data in the tb_courses table

    mysql> DELETE FROM tb_courses;
    Query OK, 3 rows affected (0.12 sec)
    mysql> SELECT * FROM tb_courses;
    Empty set (0.00 sec)

    MySQL TRUNCATE keyword

    The TRUNCATE keyword is used to completely clear a table. The syntax format is as follows:

    TRUNCATE [TABLE] 表名

    Among them, the TABLE keyword can be omitted.

    Example: Use the TRUNCATE statement to clear the records in the tb_student_course 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)

    (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 knowledge about computer programming, please visit:

    Introduction to Programming! !

The above is the detailed content of How to clear data table data in mysql. For more information, please follow other related articles on the PHP Chinese website!

Statement
The 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
How does MySQL handle concurrency compared to other RDBMS?How does MySQL handle concurrency compared to other RDBMS?Apr 29, 2025 am 12:44 AM

MySQLhandlesconcurrencyusingamixofrow-levelandtable-levellocking,primarilythroughInnoDB'srow-levellocking.ComparedtootherRDBMS,MySQL'sapproachisefficientformanyusecasesbutmayfacechallengeswithdeadlocksandlacksadvancedfeatureslikePostgreSQL'sSerializa

How does MySQL handle transactions compared to other relational databases?How does MySQL handle transactions compared to other relational databases?Apr 29, 2025 am 12:37 AM

MySQLhandlestransactionseffectivelyusingtheInnoDBengine,supportingACIDpropertiessimilartoPostgreSQLandOracle.1)MySQLusesREPEATABLEREADasthedefaultisolationlevel,whichcanbeadjustedtoREADCOMMITTEDforhigh-trafficscenarios.2)Itoptimizesperformancewithabu

How does MySQL differ from PostgreSQL?How does MySQL differ from PostgreSQL?Apr 29, 2025 am 12:23 AM

MySQLisbetterforspeedandsimplicity,suitableforwebapplications;PostgreSQLexcelsincomplexdatascenarioswithrobustfeatures.MySQLisidealforquickprojectsandread-heavytasks,whilePostgreSQLispreferredforapplicationsrequiringstrictdataintegrityandadvancedSQLf

How does MySQL handle data replication?How does MySQL handle data replication?Apr 28, 2025 am 12:25 AM

MySQL processes data replication through three modes: asynchronous, semi-synchronous and group replication. 1) Asynchronous replication performance is high but data may be lost. 2) Semi-synchronous replication improves data security but increases latency. 3) Group replication supports multi-master replication and failover, suitable for high availability requirements.

How can you use the EXPLAIN statement to analyze query performance?How can you use the EXPLAIN statement to analyze query performance?Apr 28, 2025 am 12:24 AM

The EXPLAIN statement can be used to analyze and improve SQL query performance. 1. Execute the EXPLAIN statement to view the query plan. 2. Analyze the output results, pay attention to access type, index usage and JOIN order. 3. Create or adjust indexes based on the analysis results, optimize JOIN operations, and avoid full table scanning to improve query efficiency.

How do you back up and restore a MySQL database?How do you back up and restore a MySQL database?Apr 28, 2025 am 12:23 AM

Using mysqldump for logical backup and MySQLEnterpriseBackup for hot backup are effective ways to back up MySQL databases. 1. Use mysqldump to back up the database: mysqldump-uroot-pmydatabase>mydatabase_backup.sql. 2. Use MySQLEnterpriseBackup for hot backup: mysqlbackup--user=root-password=password--backup-dir=/path/to/backupbackup. When recovering, use the corresponding life

What are some common causes of slow queries in MySQL?What are some common causes of slow queries in MySQL?Apr 28, 2025 am 12:18 AM

The main reasons for slow MySQL query include missing or improper use of indexes, query complexity, excessive data volume and insufficient hardware resources. Optimization suggestions include: 1. Create appropriate indexes; 2. Optimize query statements; 3. Use table partitioning technology; 4. Appropriately upgrade hardware.

What are views in MySQL?What are views in MySQL?Apr 28, 2025 am 12:04 AM

MySQL view is a virtual table based on SQL query results and does not store data. 1) Views simplify complex queries, 2) Enhance data security, and 3) Maintain data consistency. Views are stored queries in databases that can be used like tables, but data is generated dynamically.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

ZendStudio 13.5.1 Mac

ZendStudio 13.5.1 Mac

Powerful PHP integrated development environment

SecLists

SecLists

SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.