DISTINCT for unique values in MySQL - Mini Project: Build & Apply

Using DISTINCT to Find Unique Values in MySQL

📖 Scenario: You work at a small bookstore that keeps track of all book sales in a database. Sometimes, you want to find out which unique book titles have been sold, without counting duplicates.

🎯 Goal: Build a simple MySQL query that uses DISTINCT to list unique book titles sold from the sales table.

📋 What You'll Learn

Create a table called sales with columns id (integer), title (text), and price (decimal).

Insert the exact sales data with duplicate book titles as specified.

Write a query using DISTINCT to select unique book titles from the sales table.

Complete the final query to return only the unique titles.

💡 Why This Matters

🌍 Real World

Bookstores and many businesses use DISTINCT to find unique items sold, unique customers, or unique product categories from their sales data.

💼 Career

Knowing how to use DISTINCT is essential for data analysts and database administrators to clean data and generate accurate reports.

1

Create the sales table and insert data

Create a table called sales with columns id as INT, title as VARCHAR(100), and price as DECIMAL(5,2). Then insert these rows exactly: (1, 'The Great Gatsby', 10.99), (2, '1984', 8.99), (3, 'The Great Gatsby', 10.99), (4, 'To Kill a Mockingbird', 7.99), (5, '1984', 8.99).

MySQL

-- Create the sales table and insert the data below
-- Your code here

Need a hint?

Use CREATE TABLE to define the table and INSERT INTO to add rows.

2

Set up the SELECT statement to get book titles

Write a SELECT statement that selects the title column from the sales table. Assign this query to a variable called query.

MySQL

CREATE TABLE sales (
  id INT,
  title VARCHAR(100),
  price DECIMAL(5,2)
);

INSERT INTO sales (id, title, price) VALUES
(1, 'The Great Gatsby', 10.99),
(2, '1984', 8.99),
(3, 'The Great Gatsby', 10.99),
(4, 'To Kill a Mockingbird', 7.99),
(5, '1984', 8.99);

-- Write a SELECT statement to get the title column
SET @query = 'SELECT title FROM sales';

Need a hint?

Use SET @query = 'SELECT title FROM sales' to store the query as a string.

3

Modify the SELECT statement to use DISTINCT

Change the @query variable to select only unique title values using DISTINCT from the sales table.

MySQL

CREATE TABLE sales (
  id INT,
  title VARCHAR(100),
  price DECIMAL(5,2)
);

INSERT INTO sales (id, title, price) VALUES
(1, 'The Great Gatsby', 10.99),
(2, '1984', 8.99),
(3, 'The Great Gatsby', 10.99),
(4, 'To Kill a Mockingbird', 7.99),
(5, '1984', 8.99);

-- Modify the query to select distinct titles
SET @query = 'SELECT DISTINCT title FROM sales';

Need a hint?

Add the keyword DISTINCT right after SELECT to get unique titles.

4

Complete the query to return unique book titles

Finalize the query by writing a SELECT statement that returns unique title values from the sales table using DISTINCT. This is the final query you will run.

MySQL

CREATE TABLE sales (
  id INT,
  title VARCHAR(100),
  price DECIMAL(5,2)
);

INSERT INTO sales (id, title, price) VALUES
(1, 'The Great Gatsby', 10.99),
(2, '1984', 8.99),
(3, 'The Great Gatsby', 10.99),
(4, 'To Kill a Mockingbird', 7.99),
(5, '1984', 8.99);

-- Write the final SELECT query to get unique titles
SELECT DISTINCT title FROM sales;

Need a hint?

Use SELECT DISTINCT title FROM sales; to get the unique book titles.