SQL DISTINCT

In SQL, the DISTINCT keyword is used in the SELECT statement to retrieve unique values from a database table. Any value that has a duplicate will only show up once.

Syntax

SELECT DISTINCT "column_name"
FROM "table_name";

"table_name" is the name of the table where data is stored, and "column_name" is the name of the column containing the data to be retrieved.

Examples

The examples will use the following table:

Table Store_Information

Example 1: Use DISTINCT on one column

To select all distinct stores in Table Store_Information, we key in,

SELECT DISTINCT Store_Name FROM Store_Information;

Result:

Example 2: Use DISTINCT on multiple columns

We can apply DISTINCT to multiple columns. If we want to get a list showing all unique combinations of stores and transaction dates, we would type in the following,

SELECT DISTINCT Store_Name, Txn_Date FROM Store_Information;

Result:

Exercises

For these exercises, assume we have a table called Users with the following data:

Table Users

1. Which of the following SQL statement is valid?
a) SELECT DISTINCT * FROM Users;
b) SELECT DISTINCT First_Name FROM Users;
c) SELECT DISTINCT First_Name Last_Name FROM Users;

2. What's the result of the following query?
SELECT DISTINCT Join_Date From Users;

3. What's the result of the following query?
SELECT DISTINCT Gender, Join_Date From Users;