What is the DISTINCT command and what is it used for?

The DISTINCT command in SQL is used to select only unique (non-repeating) values from a specified column or set of columns in the query results SELECT.

Usage:

• Removing duplicates in the result set.
• Getting a list of all unique values from a column (for example, a list of all different cities, customers, etc.).

Example of usage:

-- Select all unique cities from the "Customers" table
SELECT DISTINCT City
FROM Customers;

-- Select unique combinations of city and country from the "Customers" table
SELECT DISTINCT City, Country
FROM Customers;