SQL SELECT DISTINCT Statement

How do I return unique values in SQL?

SELECT DISTINCT returns only distinct (i.e. different) values.
SELECT DISTINCT eliminates duplicate records from the results.
DISTINCT can be used with aggregates: COUNT, AVG, MAX, etc.
DISTINCT operates on a single column. DISTINCT for multiple columns is not supported.

The general syntax is

SELECT DISTINCT column-name
  FROM table-name

Can be used with COUNT and other aggregates

SELECT COUNT (DISTINCT column-name)
  FROM table-name

Problem: List all unique supplier countries in alphabetical order.

SELECT DISTINCT Country
  FROM Supplier
ORDER BY COUNTRY

Result: 16 rows

Problem: List the number of unique supplier countries

SELECT COUNT (DISTINCT Country)
  FROM Supplier

Result:

Count
16