MySQL DISTINCT Clause (original) (raw)

Last Updated : 23 Mar, 2026

The SELECT DISTINCT statement is used to retrieve unique values from one or more columns in a table. It removes duplicate records and returns only distinct results.

• It helps in eliminating duplicate data.
• It can be used with one or multiple columns.
• It is useful for data analysis and filtering unique entries.

**Syntax:

SELECT DISTINCT column1, column2, ...FROM table_nameWHERE condition;

• **column1, column2, ... : Columns from which distinct values are selected.
• **table_name: Name of the table from which data is retrieved.
• **condition: Optional filter to select specific rows.

Examples of DISTINCT Clause

These examples show how to use DISTINCT to get unique values from a table.

Example 1: Selecting Distinct Values from a Single Column

Consider a table named employees with the following data:

To retrieve a list of unique departments, you can use the DISTINCT clause:

SELECT DISTINCT department FROM employees;

**Output:

• This query returns a list of unique departments from the employees table, eliminating any duplicates.

Example 2: Selecting Distinct Values From Multiple Columns

Suppose you want to retrieve unique combinations of department and employee_name. You can modify the query to include multiple columns:

SELECT DISTINCT department, employee_name FROM employees;

**Output:

• In this case, the query returns distinct combinations of department and employee_name.

Example 3: Using DISTINCT with WHERE Clause

DISTINCT clause can be combined with the WHERE clause to filter results. For example, to get unique departments that start with 'S':

SELECT DISTINCT department FROM employees WHERE department LIKE 'S%';

**Output:

• This query filters the departments to only those starting with 'S' and then returns unique values.

**Things to Remember When Using DISTINCT

The following points highlight important aspects to consider when using the DISTINCT clause in MySQL.

• **Performance Impact: DISTINCT can slow down queries on large datasets as MySQL must compare rows to remove duplicates.
• **Order of Columns: Uniqueness depends on the order of columns in the SELECT statement.
• **NULL Values: Multiple NULL values are treated as duplicates.