Home Database Mysql Tutorial How to modify the index type in mysql

How to modify the index type in mysql

Apr 14, 2022 pm 07:50 PM
mysql

Mysql method to modify the index type: 1. Use the "DROP INDEX index name ON table name;" statement to delete the original specified index; 2. Use "CREATE index type keyword INDEX index name ON table name (column Name [length])" statement creates an index with the same name to modify the type.

How to modify the index type in mysql

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

There is no direct instruction to modify the index in MySQL. Generally, we need to delete the original index first, and then create an index with the same name as needed, so as to modify the index in disguise.

mysql Modify index type

#1. Delete the original index

When the index is no longer needed , you can use the DROP INDEX statement to delete the index.

Grammar format:

DROP INDEX <索引名> ON <表名>
Copy after login

The syntax description is as follows:

  • : The name of the index to be deleted.

  • : Specify the table name where the index is located.

    Example:

    tb_stu_info2 Index information of the data table

    How to modify the index type in mysql

    It can be seen from the output results : "Key_name: height"--The name of the index is "height", "Index_type: BTREE"-The type used by the index is "BTREE"

    Delete the index height in the table tb_stu_info2

    DROP INDEX height ON tb_stu_info2;
    Copy after login

    2. Create an index with the same name

    You can use the CREATE INDEX statement specifically used to create an index to create an index on an existing table, but this statement cannot create a primary key.

    Syntax format:

    CREATE <索引名> INDEX ON <表名> (<列名> [<长度>] [ ASC | DESC])
    Copy after login

    The syntax description is as follows:

    • : Specify the index name. A table can create multiple indexes, but each index has a unique name in the table.

    : Specify the name of the table to create an index.

  • : Specify the column name to create an index. You can usually consider using columns that frequently appear in the JOIN clause and WHERE clause in the query statement as index columns.

  • : Optional. Specifies that the length characters preceding the column are used to create the index. Creating an index using part of a column can help reduce the size of the index file and save the space occupied by the index columns. In some cases, only the prefix of a column can be indexed. The length of an index column has a maximum limit of 255 bytes (1000 bytes for MyISAM and InnoDB tables). If the length of an index column exceeds this limit, it can only be indexed using the column's prefix. In addition, columns of type BLOB or TEXT must also use prefix indexes.

  • ASC|DESC: Optional. ASC specifies that the index is sorted in ascending order, DESC specifies that the index is sorted in descending order, and the default is ASC.

  • Example:

    • Create a normal index

    CREATE INDEX height ON tb_stu_info2 (height(8));
    Copy after login
    • When creating a unique index, the UNIQUE keyword is usually used.

    CREATE UNIQUE INDEX height ON tb_stu_info2 (height(8));
    Copy after login

    Expand knowledge:

    The index types in MySQL are as follows

    • General Index

    • Unique index

    • Primary key index

    • Combined index

    • Full text index

    [Related recommendations: mysql video tutorial]

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

    Statement of this Website
    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

    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

    AI Hentai Generator

    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
    Repo: How To Revive Teammates
    4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
    Hello Kitty Island Adventure: How To Get Giant Seeds
    3 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

    Hot Tools

    Notepad++7.3.1

    Notepad++7.3.1

    Easy-to-use and free code editor

    SublimeText3 Chinese version

    SublimeText3 Chinese version

    Chinese version, very easy to use

    Zend Studio 13.0.1

    Zend Studio 13.0.1

    Powerful PHP integrated development environment

    Dreamweaver CS6

    Dreamweaver CS6

    Visual web development tools

    SublimeText3 Mac version

    SublimeText3 Mac version

    God-level code editing software (SublimeText3)

    PHP's big data structure processing skills PHP's big data structure processing skills May 08, 2024 am 10:24 AM

    Big data structure processing skills: Chunking: Break down the data set and process it in chunks to reduce memory consumption. Generator: Generate data items one by one without loading the entire data set, suitable for unlimited data sets. Streaming: Read files or query results line by line, suitable for large files or remote data. External storage: For very large data sets, store the data in a database or NoSQL.

    How to optimize MySQL query performance in PHP? How to optimize MySQL query performance in PHP? Jun 03, 2024 pm 08:11 PM

    MySQL query performance can be optimized by building indexes that reduce lookup time from linear complexity to logarithmic complexity. Use PreparedStatements to prevent SQL injection and improve query performance. Limit query results and reduce the amount of data processed by the server. Optimize join queries, including using appropriate join types, creating indexes, and considering using subqueries. Analyze queries to identify bottlenecks; use caching to reduce database load; optimize PHP code to minimize overhead.

    How to use MySQL backup and restore in PHP? How to use MySQL backup and restore in PHP? Jun 03, 2024 pm 12:19 PM

    Backing up and restoring a MySQL database in PHP can be achieved by following these steps: Back up the database: Use the mysqldump command to dump the database into a SQL file. Restore database: Use the mysql command to restore the database from SQL files.

    How to insert data into a MySQL table using PHP? How to insert data into a MySQL table using PHP? Jun 02, 2024 pm 02:26 PM

    How to insert data into MySQL table? Connect to the database: Use mysqli to establish a connection to the database. Prepare the SQL query: Write an INSERT statement to specify the columns and values ​​to be inserted. Execute query: Use the query() method to execute the insertion query. If successful, a confirmation message will be output.

    How to fix mysql_native_password not loaded errors on MySQL 8.4 How to fix mysql_native_password not loaded errors on MySQL 8.4 Dec 09, 2024 am 11:42 AM

    One of the major changes introduced in MySQL 8.4 (the latest LTS release as of 2024) is that the &quot;MySQL Native Password&quot; plugin is no longer enabled by default. Further, MySQL 9.0 removes this plugin completely. This change affects PHP and other app

    How to use MySQL stored procedures in PHP? How to use MySQL stored procedures in PHP? Jun 02, 2024 pm 02:13 PM

    To use MySQL stored procedures in PHP: Use PDO or the MySQLi extension to connect to a MySQL database. Prepare the statement to call the stored procedure. Execute the stored procedure. Process the result set (if the stored procedure returns results). Close the database connection.

    How to create a MySQL table using PHP? How to create a MySQL table using PHP? Jun 04, 2024 pm 01:57 PM

    Creating a MySQL table using PHP requires the following steps: Connect to the database. Create the database if it does not exist. Select a database. Create table. Execute the query. Close the connection.

    The difference between oracle database and mysql The difference between oracle database and mysql May 10, 2024 am 01:54 AM

    Oracle database and MySQL are both databases based on the relational model, but Oracle is superior in terms of compatibility, scalability, data types and security; while MySQL focuses on speed and flexibility and is more suitable for small to medium-sized data sets. . ① Oracle provides a wide range of data types, ② provides advanced security features, ③ is suitable for enterprise-level applications; ① MySQL supports NoSQL data types, ② has fewer security measures, and ③ is suitable for small to medium-sized applications.

    See all articles