What are the different types of MySQL indexes?

MySQL index is an important tool to improve query efficiency, it can speed up data retrieval. Several common indexes in MySQL are introduced in detail below, and specific code examples are provided.

1. Primary Key Index:
   The primary key index is a special unique index used to uniquely identify a record. Each table can only have one primary key, and the value of the primary key index cannot be NULL.

Sample code:
CREATE TABLE student (
id INT PRIMARY KEY,
name VARCHAR(50),
age INT
);

2. Unique Index:
   The unique index ensures that the value in the index column is unique, which can speed up the search and update operations of the column.

Sample code:
CREATE TABLE student (
id INT,
name VARCHAR(50),
age INT,
UNIQUE INDEX idx_name (name)
);

3. Normal Index:
   Normal index is the most common index type and is used to speed up column search and sort operations.

Sample code:
CREATE TABLE student (
id INT,
name VARCHAR(50),
age INT,
INDEX idx_age (age)
);

4. Fulltext Index:
   Fulltext Index is used to perform full-text search on text fields, which can improve the efficiency of text search.

Sample code:
CREATE TABLE articles (
id INT,
title VARCHAR(100),
content TEXT,
FULLTEXT INDEX idx_content (content)
);

5. Composite Index:
   The composite index is an index composed of multiple columns, which can improve the query efficiency of multiple column combination conditions.

Sample code:
CREATE TABLE book (
id INT,
title VARCHAR(100),
author VARCHAR(50),
price DECIMAL(8 ,2),
INDEX idx_title_author_price (title, author, price)
);

6. Spatial Index:
   Spatial index is used to speed up queries on spatial data , such as geographical location information.

Sample code:
CREATE TABLE locations (
id INT,
name VARCHAR(100),
location POINT,
SPATIAL INDEX idx_location (location)
);

7. Hash Index:
   Hash index uses a hash algorithm to convert the value of the index column into a hash value, which can speed up equal-value queries, but does not Support range query.

Sample code:
CREATE TABLE user (
id INT,
name VARCHAR(50),
age INT,
HASH INDEX idx_age (age)
);

The above are several index types commonly used in MySQL. Different index types are suitable for different query scenarios. In practical applications, selecting the appropriate index type according to specific needs and data characteristics can effectively improve the query efficiency of the database.

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