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The SELECT DISTINCT statement is used to return only distinct (different) values
The SELECT DISTINCT
statement is used to return only distinct
(different) values.
Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.
SELECT DISTINCT Syntax
SELECT DISTINCT column1, column2, ...
FROM table_name;
Below is a selection from the "Customers" table in the Northwind sample 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 |
The following SQL statement selects all (including the duplicates) values from the "Country" column in the "Customers" table:
SELECT Country FROM Customers;
Now, let us use the SELECT DISTINCT
statement and see the result.
The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table:
SELECT DISTINCT Country FROM Customers;
The following SQL statement lists the number of different (distinct) customer countries:
SELECT COUNT(DISTINCT Country) FROM Customers;
Note: The example above will not work in Firefox! Because COUNT(DISTINCT column_name) is not supported in Microsoft Access databases. Firefox is using Microsoft Access in our examples.
Here is the workaround for MS Access:
SELECT Count(*) AS DistinctCountries
FROM (SELECT DISTINCT Country FROM Customers);
Select all the different values from the Country
column in the Customers
table.
Country
FROM Customers;