When you need to ensure that every record in your database is uniquely identifiable not just within a single table, but across distributed systems or even globally, the UUID (Universally Unique Identifier) data type is a powerful solution. A UUID is a 128-bit value, typically represented as a string of hexadecimal digits separated by hyphens, such as 550e8400-e29b-41d4-a716-446655440000. This structure allows for an enormous number of possible values—so many that the chance of accidental duplication is practically zero. Unlike simple integer-based identifiers, UUIDs are designed to be unique even if records are created independently on different servers or systems. This makes them especially valuable in applications that require merging data from multiple sources, syncing across distributed databases, or generating identifiers client-side before data ever reaches the database.

CREATE TABLE users (
    user_id UUID PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL
);

In the table definition above, the user_id column uses the UUID data type and serves as the primary key. By doing so, you ensure that each user is assigned a globally unique identifier. UUIDs are typically generated using algorithms that combine factors like the current timestamp, hardware addresses, random numbers, and more, depending on the UUID version. Many programming languages and database systems provide built-in functions to generate UUIDs, so you do not have to create them manually. When you insert a new record, you can generate a UUID in your application code or use a database function to do it directly in SQL. This approach is particularly useful for distributed applications, where multiple systems might be creating records at the same time and you need to avoid key collisions.

INSERT INTO users (user_id, username, email)
VALUES ('f47ac10b-58cc-4372-a567-0e02b2c3d479', 'jane_doe', 'jane@example.com');

In this example, a new user is inserted into the users table with a specific UUID as the unique identifier. This value could have been generated by your application or by the database itself. By using UUIDs, you gain the flexibility to create records in different locations or at different times without worrying about duplicate primary keys. This is why UUIDs are a popular choice for systems that require robust, scalable, and globally unique identifiers.