Unique Index - (PostgreSQL Indexes)

An index is a database structure used to improve the speed of data retrieval operations on database tables. In PostgreSQL, a unique index is used to enforce uniqueness of data in a table. In this tutorial, we'll show you how to use a unique index in PostgreSQL.

Syntax

CREATE UNIQUE INDEX idx_name
ON table_name (column1, column2, ...);

• idx_name: The name of the index to create.
• table_name: The name of the table to create the index for.
• (column1, column2, ...): The list of columns to create the index for.

Example

Let's take a look at an example of creating a unique index in PostgreSQL.

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    CONSTRAINT email_unique UNIQUE (email)
);

In this example, we created a users table with columns for id, username, and email. The email column is marked as UNIQUE, which creates a unique index on that column.

Explanation

A unique index is used to enforce uniqueness of data in a table. When a unique index is created on a column or set of columns, the database system ensures that no two rows in the table have duplicate values in those columns. This can prevent data inconsistencies and improve data retrieval performance.

In our example, we created a users table with a unique index on the email column. This ensures that each email address entered into the table is unique.

Use

A unique index is useful when you want to ensure that values in a column or set of columns are unique. This can be useful for columns such as email addresses, usernames, or primary keys in a table.

Important Points

• A unique index is created with the CREATE UNIQUE INDEX statement.
• A unique index can be created on one or more columns in a table.
• A unique index prevents duplicate values from being inserted into a table.

Summary

In this tutorial, we showed you how to use a unique index in PostgreSQL. We covered the syntax, example, output, explanation, use, and important points of using a unique index. With this knowledge, you can now use a unique index to ensure that values in a column or set of columns are unique in PostgreSQL.