Summary: this tutorial introduces you to MySQL UUID, shows you to use it as the primary key (PK) for a table, and discusses the pros and cons of using it as the primary key.

Introduction to MySQL UUID

UUID stands for Universally Unique IDentifier. UUID is defined based on RFC 4122, “a Universally Unique Identifier (UUID) URN Namespace).

UUID is designed as a number that is unique globally in space and time. Two UUID values are expected to be distinct, even they are generated on two independent servers.

In MySQL, a UUID value is a 128-bit number represented as a utf8 string of five hexadecimal numbers in the following format:

Code language: SQL (Structured Query Language) (sql)

To generate UUID values, you use the UUID() function as follows:

Code language: SQL (Structured Query Language) (sql)

The UUID() function returns a UUID value in compliance with UUID version 1 described in the RFC 4122.

For example, the following statement uses the UUID() function to generate a UUID value:

Code language: SQL (Structured Query Language) (sql)

MySQL UUID vs. Auto-Increment INT as primary key

Pros

Using UUID for a primary key  brings the following advantages:

• UUID values are unique across tables, databases, and even servers that allow you to merge rows from different databases or distribute databases across servers.
• UUID values do not expose the information about your data so they are safer to use in a URL. For example, if a customer with id 10 accesses his account via http://www.example.com/customers/10/ URL, it is easy to guess that there is a customer 11, 12, etc., and this could be a target for an attack.
• UUID values can be generated anywhere that avoid a round trip to the database server. It also simplifies logic in the application. For example, to insert data into a parent table and child tables, you have to insert into the parent table first, get generated id and then insert data into the child tables. By using UUID, you can generate the primary key value of the parent table up front and insert rows into both parent and child tables at the same time within a transaction.

Cons

Besides the advantages, UUID values also come with some disadvantages:

• Storing UUID values (16-bytes) takes more storage than integers (4-bytes) or even big integers(8-bytes).
• Debugging seems to be  more difficult, imagine the expression WHERE id = 'df3b7cb7-6a95-11e7-8846-b05adad3f0ae' instead of WHERE id = 10
• Using UUID values may cause performance issues due to their size and not being ordered.

MySQL UUID solution

In MySQL, you can store UUID values in a compact format (BINARY) and display them in human-readable format (VARCHAR) with help of the following functions:

• UUID_TO_BIN
• BIN_TO_UUID
• IS_UUID

The UUID_TO_BIN() function converts a UUID from a human-readable format (VARCHAR) into a compact format (BINARY) format for storing and the BIN_TO_UUID() function converts UUID from the compact format (BINARY)to human-readable format (VARCHAR) for displaying.

The IS_UUID() function returns 1 if the argument is a valid string-format UUID. If the argument is not valid string format UUID, the IS_UUID function returns 0. In case the argument is NULL, the IS_UUID() function returns NULL.

The following are the valid string-format UUID in MySQL:

Code language: SQL (Structured Query Language) (sql)

MySQL UUID example

Let’s take a look at an example of using UUID as the primary key.

The following statement creates a new table named customers:

Code language: SQL (Structured Query Language) (sql)

To insert UUID values into the id column, you use UUID() and UUID_TO_BIN() functions as follows:

Code language: SQL (Structured Query Language) (sql)

To query data from a UUID column, you use BIN_TO_UUID() function to convert binary format to human-readable format:

Code language: SQL (Structured Query Language) (sql)

In this tutorial, you have learned about MySQL UUID and how to use it for the primary key column.