SQLite: DISTINCT Clause

This SQLite post explains how to use the SQLite DISTINCT clause with syntax and examples.

Description

The SQLite DISTINCT clause is used to remove duplicates from the result set. The DISTINCT clause can only be used with SELECT statements.

Syntax

The syntax for the DISTINCT clause in SQLite is:

SELECT DISTINCT expressions
FROM tables
[WHERE conditions];

Parameters or Arguments

expressions

The columns or calculations that you wish to retrieve.

tables

The tables that you wish to retrieve records from. There must be at least one table listed in the FROM clause.

WHERE conditions

Optional. The conditions that must be met for the records to be selected.

Note

• When only one expression is provided in the DISTINCT clause, the query will return the unique values for that expression.
• When more than one expression is provided in the DISTINCT clause, the query will retrieve unique combinations for the expressions listed.
• In SQLite, the DISTINCT clause doesn't ignore NULL values. So when using the DISTINCT clause in your SQL statement, your result set will include NULL as a distinct value.

Example - With Single Expression

Let's look at the simplest example of how to use the DISTINCT clause in SQLite. We can use the DISTINCT clause to remove duplicates from our result set, which is comprised of just a single field.

For example:

SELECT DISTINCT last_name
FROM employees;

This SQLite DISTINCT example would return all unique last_name values from the employees table.

Example - With Multiple Expressions

Let's look at how you might use the SQLite DISTINCT clause to remove duplicates from more than one field in your SELECT statement.

For example:

SELECT DISTINCT last_name, first_name
FROM employees;

This SQLite DISTINCT clause example would return each unique last_name and first_name combination from the employees table. In this case, the DISTINCT applies to each field listed after the DISTINCT keyword, and therefore returns distinct combinations.