Clustered Index - (MySQL Indexes)

In MySQL, a clustered index is an index that determines the physical order of data in a table. In this tutorial, we'll discuss what a clustered index is, how to create one, and when to use it.

Syntax

To create a clustered index in MySQL, you can use the following syntax:

ALTER TABLE table_name ADD PRIMARY KEY (column_name);

Note that creating a clustered index automatically creates a unique index on the same column(s).

Example

Let's say we have a table called "customers" with columns for customer ID, name, email, and phone number. We want to create a clustered index on the customer ID column to improve query performance. Here's how we can implement it:

ALTER TABLE customers ADD PRIMARY KEY (customer_id);

Explanation

In the example above, we created a clustered index on the customer ID column in the customers table. This means that the rows in the table are physically stored in ascending order based on the customer ID column. This can improve the performance of queries that involve searching, sorting, or grouping on the customer ID column.

Use

A clustered index can be useful for improving the performance of queries that involve searching, sorting, or grouping on a specific column. Because the rows in the table are physically ordered based on the clustered index, queries that involve the indexed column can be performed more efficiently.

Important Points

• A clustered index determines the physical order of data in a table based on the indexed column.
• A table can have only one clustered index.
• A clustered index can improve query performance for queries that involve the indexed column.
• Using a clustered index can result in slower performance for updates, inserts, and deletes, as the rows may need to be physically reordered.

Summary

In this tutorial, we discussed what a clustered index is, how to create one in MySQL, and when to use it. A clustered index can be useful for improving the performance of queries that involve searching, sorting, or grouping on a specific column, but it can result in slower performance for updates, inserts, and deletes. Understanding how to use clustered indexes can help you optimize your MySQL database for better performance.