SQL Tutorial
SQL Select Distinct
The SQL SELECT DISTINCT Statement
To retrieve just distinct (different) data, use the SELECT DISTINCT command.
Example
Select all the different countries from the “Customers” table:
SELECT DISTINCT Country FROM Customers;
A column in a database may have a lot of duplicate entries, and there may be instances when you just want to list the unique values.
Syntax
SELECT DISTINCT column1, column2, …
FROM table_name;
Demo Database
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 |
Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
| 4 |
Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
| 5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |
SELECT Example Without DISTINCT
The SQL statement returns the “Country” value from each record in the “Customers” table if the DISTINCT clause is left out:
Example
SELECT Country FROM Customers;
Count Distinct
We may retrieve the total number of distinct countries by utilizing the DISTINCT keyword in the COUNT function.
Example
SELECT COUNT(DISTINCT Country) FROM Customers;
Note: Microsoft Access databases do not support COUNT(DISTINCT column_name).
An MS Access workaround is provided here:
Example
SELECT Count(*) AS DistinctCountries
FROM (SELECT DISTINCT Country FROM Customers);
The COUNT function will be covered later in this tutorial.
