You will often encounter situations where standard SQL data types are not enough to represent certain kinds of information efficiently. Special data types such as BOOLEAN, UUID, and ARRAY are designed for these cases. Each of these types serves a unique purpose and can make your database design more expressive and robust.

The BOOLEAN type is used to represent truth values—either TRUE or FALSE. This is ideal for flags such as whether a user is verified, active, or has accepted terms and conditions. The UUID (Universally Unique Identifier) type is used for storing unique identifiers that are extremely unlikely to collide, even across distributed systems. This is especially useful for user IDs or transaction IDs that must be unique across many databases or services. The ARRAY type allows you to store a list of values in a single column, such as multiple tags or categories associated with a record.

Let's see how you can use these special data types in a table definition.

CREATE TABLE users (
    is_verified BOOLEAN,
    user_id UUID,
    tags VARCHAR(50)[]
);

In this table, the is_verified column uses the BOOLEAN type to indicate whether a user has verified their account. The user_id column uses the UUID type to store a globally unique identifier for each user. The tags column uses an ARRAY of VARCHAR values, allowing you to associate a flexible list of tags with each user.

Choosing the right special data type depends on your data modeling needs. Use BOOLEAN when you need to store true/false values, such as feature toggles or status indicators. Use UUID when you need unique, non-sequential identifiers that are difficult to guess and safe to generate in distributed systems. Use ARRAY when you want to store multiple related values—such as tags, categories, or preferences—in a single column, making it easier to query and update sets of values associated with a record.

Next, see how you can insert data into these columns using the appropriate syntax for each special type.

INSERT INTO users (is_verified, user_id, tags) VALUES
(TRUE, '550e8400-e29b-41d4-a716-446655440000', ARRAY['admin', 'editor']),
(FALSE, '550e8400-e29b-41d4-a716-446655440001', ARRAY['viewer']),
(TRUE, '550e8400-e29b-41d4-a716-446655440002', ARRAY['admin', 'subscriber', 'beta']);