SQL SELECT DISTINCT Statement

The SQL SELECT DISTINCT Statement is used to retrieve unique records (by removing the duplicates) from the specified Column in the SELECT Statement.

In this article, we will show you, How to write SQL Select Distinct with an example. The basic syntax of the SQL Server SELECT DISTINCT can be written as:

-- SQL Server SELECT DISTINCT Statement
SELECT DISTINCT [Column Names]
FROM Source
WHERE Conditions -- This is Optional

DISTINCT: Returns Unique Columns in Sql
Columns: It allows us to choose the number of columns from the tables. It may be One or more.
Source: One or more tables present in the Database. JOINS are used to join multiple tables in SQL Server.

We are going to use the below-shown data to explain the SQL Server Select Distinct with an example.

SQL Select Distinct Single Column

In this example, We are going to select the unique records present in the Education Column.

-- SQL Select Distinct on Single Column Example
USE [SQLTEST]
GO
SELECT DISTINCT [Education]
  FROM [Employees]

OUTPUT

SQL Select Distinct Multiple Columns

When we use the Select Distinct multiple columns, the SELECT Statement returns the unique combination of multiple columns instead of unique individual records.

In this example, We are going to select the unique combination records present in the Education Column and Yearly Income Column.

-- SQL Select Distinct Multiple Columns Example
SELECT DISTINCT [Education]
 ,[YearlyIncome]
  FROM [Employees]

OUTPUT

Although we used the DISTINCT Keyword in the SELECT Statement, from the above screenshot you can observe that it is returning duplicates because

Bachelors and 70000 is a Unique Combination
Bachelors and 80000 is a Unique Combination
and Bachelors and 90000 is a Unique Combination

SQL DISTINCT WHERE Clause

In this example, we will show you, How to use the Select distinct along with WHERE Clause. The following Sql unique statement will return the Distinct Education values whose Yearly Income is greater than 50000

-- SQL Select Distinct Where Example
SELECT DISTINCT [Education]
 ,[YearlyIncome]
  FROM [Employees]
  WHERE YearlyIncome > 50000

OUTPUT

NOTE: The SQL DISTINCT consider the NULL records as a valid unique record. So, Please use any Not Null function (NOT NULL) functions to remove NULLS.

SQL Distinct Group By Example

The SQL Server Distinct also allows you to use Aggregate Functions along with Group By Clause.

The following Sql unique query groups the employees by Education. Next, it finds the Sum of Distinct Yearly Income for each Education group.

-- SQL Select Distinct Group By Example
SELECT [Education]
 ,SUM(DISTINCT  YearlyIncome) AS [Total Income]
  FROM [Employees]
  GROUP BY [Education]

OUTPUT

Let me remove the Distinct Keyword from the above query.

-- SQL Select Distinct Group By Example
SELECT [Education]
 ,SUM(YearlyIncome) AS [Total Income]
  FROM [Employees]
  GROUP BY [Education]

From the below screenshot you can see the difference in yearly Income. Because it is finding the sum of all the records (not the Distinct ones).

Distinct Count Example 1

This SQL Select Distinct Count is one of the most commonly asked questions. This example counts and returns the distinct employee Ids in each Education group.

-- SQL Select Distinct Count Example
SELECT [Education]
 ,COUNT(DISTINCT EmpID) AS [Total Employees]
  FROM [Employees]
  GROUP BY [Education]

OUTPUT

SQL Select Distinct Count Example 2

Here, we used Count Function with the Distinct keyword, and without Distinct. This Sql unique example will show the difference between the result set.

-- SQL Select Distinct Count Example
SELECT [Education]
 ,COUNT(DISTINCT DeptID) AS [Total Dept Ids]
 ,COUNT(DeptID) AS [Total Ids]
  FROM [Employees]
  GROUP BY [Education]

OUTPUT

Select Distinct Null Example

The Sql Server Select Distinct statement considers NULL as a distinct one. You can see the same in below example.

-- SQL Select Distinct Example
SELECT DISTINCT DeptID
  FROM [Employees]

OUTPUT