What types of mysql indexes are there?
The main index types currently available in MySQL are: ordinary index, unique index, primary key index, combined index, and full-text index. The following article will introduce these MySQL indexes to you, I hope it will be helpful to you.
#By adding indexes to fields, you can increase the speed of data reading and improve the concurrency and stress resistance of the project. Index optimization is an optimization method in MySQL. The index is equivalent to the table of contents of a book. You can quickly find the required content based on the page numbers in the table of contents.
Let’s take a look at the main index types currently available in MySQL:
1. Ordinary index
Ordinary index is the most basic index. There are no restrictions, the value can be empty; only speeds up queries. It can be created or deleted in the following ways:
1), directly creating an index
CREATE INDEX index_name ON table(column(length))
2), adding an index by modifying the table structure
ALTER TABLE table_name ADD INDEX index_name ON (column(length))
3), Delete index
DROP INDEX index_name ON table
2. Unique index
The unique index is similar to the ordinary index, except that the value of the index column must be unique, but empty is allowed value. In the case of a composite index, the combination of column values must be unique. To put it simply: a unique index speeds up queries because the column value is unique (can have null). It can be created in the following ways:
1), creating a unique index
CREATE UNIQUE INDEX indexName ON table(column(length))
2), modifying the table structure
ALTER TABLE table_name ADD UNIQUE indexName ON (column(length))
3, primary key index
The primary key index is a special unique index. A table can only have one primary key and no null values are allowed. To put it simply: the primary key index speeds up queries. The column value is unique (cannot have null) and there is only one in the table.
Generally, the primary key index is created at the same time when creating the table:
CREATE TABLE mytable( ID INT NOT NULL, username VARCHAR(16) NOT NULL, PRIMARY KEY(ID) );
Of course, you can also use the ALTER command. Remember: a table can only have one primary key.
4. Composite index
Combined index refers to an index created on multiple fields. Only the first field when creating the index is used in the query conditions. The index will be used. Follow the leftmost prefix set when using combined indexes.
It can be said that the combined index is an index composed of multiple column values, specially used for combined searches, and its efficiency is greater than index merging.
ALTER TABLE `table` ADD INDEX name_city_age (name,city,age);
5. Full-text index
Full-text index is mainly used to find keywords in the text, rather than directly comparing them with values in the index. The fulltext index is very different from other indexes. It is more like a search engine rather than a simple parameter matching of the where statement. The fulltext index is used with the match against operation instead of the general where statement plus like. It can be used in create table, alter table, and create index, but currently only full-text indexes can be created on char, varchar, and text columns. It is worth mentioning that when the amount of data is large, it is better to put the data into a table without a global index and then use CREATE index to create a fulltext index than to first create a fulltext for a table and then write the data. The speed is much faster.
1), it is suitable to add a full-text index when creating a table
CREATE TABLE `table` (
`id` int(11) NOT NULL AUTO_INCREMENT ,
`title` char(255) CHARACTER NOT NULL ,
`content` text CHARACTER NULL ,
`time` int(10) NULL DEFAULT NULL ,
PRIMARY KEY (`id`),
FULLTEXT (content)
);2), modify the table structure to add a full-text index
ALTER TABLE article ADD FULLTEXT index_content(content)
3), create an index directly
CREATE FULLTEXT INDEX index_content ON article(content)
Simply put: full-text indexing is to segment the text content and search.
The above is the detailed content of What types of mysql indexes are there?. For more information, please follow other related articles on the PHP Chinese website!
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
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
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.
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
MySQL's Role: Databases in Web Applications
Apr 17, 2025 am 12:23 AM
The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.
How to start mysql by docker
Apr 15, 2025 pm 12:09 PM
The process of starting MySQL in Docker consists of the following steps: Pull the MySQL image to create and start the container, set the root user password, and map the port verification connection Create the database and the user grants all permissions to the database
Laravel Introduction Example
Apr 18, 2025 pm 12:45 PM
Laravel is a PHP framework for easy building of web applications. It provides a range of powerful features including: Installation: Install the Laravel CLI globally with Composer and create applications in the project directory. Routing: Define the relationship between the URL and the handler in routes/web.php. View: Create a view in resources/views to render the application's interface. Database Integration: Provides out-of-the-box integration with databases such as MySQL and uses migration to create and modify tables. Model and Controller: The model represents the database entity and the controller processes HTTP requests.
Solve database connection problem: a practical case of using minii/db library
Apr 18, 2025 am 07:09 AM
I encountered a tricky problem when developing a small application: the need to quickly integrate a lightweight database operation library. After trying multiple libraries, I found that they either have too much functionality or are not very compatible. Eventually, I found minii/db, a simplified version based on Yii2 that solved my problem perfectly.
How to install mysql in centos7
Apr 14, 2025 pm 08:30 PM
The key to installing MySQL elegantly is to add the official MySQL repository. The specific steps are as follows: Download the MySQL official GPG key to prevent phishing attacks. Add MySQL repository file: rpm -Uvh https://dev.mysql.com/get/mysql80-community-release-el7-3.noarch.rpm Update yum repository cache: yum update installation MySQL: yum install mysql-server startup MySQL service: systemctl start mysqld set up booting
Centos install mysql
Apr 14, 2025 pm 08:09 PM
Installing MySQL on CentOS involves the following steps: Adding the appropriate MySQL yum source. Execute the yum install mysql-server command to install the MySQL server. Use the mysql_secure_installation command to make security settings, such as setting the root user password. Customize the MySQL configuration file as needed. Tune MySQL parameters and optimize databases for performance.
