Advantages and usage of prefix index in MySQL
In the MySQL database, indexing is one of the important means to improve query efficiency. In addition to the common full-field index, there is also a special index called a prefix index. This article will introduce the advantages and usage of prefix indexes, with specific code examples.
1. What is a prefix index
The prefix index only indexes the first few characters of the field, not the entire field content. The advantage of this is that it can save index storage space, increase index creation speed, and improve query performance in some specific scenarios.
2. Advantages of prefix index
3. Usage of prefix index
The following will demonstrate the usage of prefix index through a specific table and code example.
Suppose there is a table named users
, which contains the name
field, and we want to create a prefix index for the name
field.
First, create the users
table:
CREATE TABLE users ( id INT PRIMARY KEY, name VARCHAR(100) );
Then, create a prefix index for the name
field, indexing only the first 5 characters:
CREATE INDEX idx_name ON users (name(5));
Next, we can verify the creation of the index through the following query:
EXPLAIN SELECT * FROM users WHERE name LIKE 'John%';
The execution plan of the query can be viewed through the EXPLAIN
keyword to ensure that the prefix index is correctly application.
4. Notes
When using prefix index, you need to pay attention to the following points:
5. Summary
Prefix index is an important index type in MySQL. By only indexing the first few characters of the field, you can save storage space, improve index creation speed, and optimize query performance in specific scenarios. In actual applications, you need to decide whether to use a prefix index according to the specific situation, and pay attention to choosing an appropriate prefix length.
The above is an introduction to the advantages and usage of prefix indexes in MySQL. I hope it will be helpful to readers.
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