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 SQL SELECT DISTINCT syntax

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

SUPPLIER
Id
CompanyName
ContactName
City
Country
Phone
Fax

SQL SELECT Examples

Problem: List all unique supplier countries in alphabetical order.
SELECT DISTINCT Country
  FROM Supplier
ORDER BY COUNTRY
Result: 16 rows
Country
Australia
Brazil
Canada
Denmark

SUPPLIER
Id
CompanyName
ContactName
City
Country
Phone
Fax
Problem: List the number of unique supplier countries
SELECT COUNT (DISTINCT Country)
  FROM Supplier
Result:
Count
16


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