Why combining result sets is useful in MySQL - See It in Action

Why Combining Result Sets is Useful

📖 Scenario: You work at a small bookstore that tracks sales in two separate tables: online_sales and store_sales. You want to see all sales together to understand total sales better.

🎯 Goal: Build a combined list of all sales from both online_sales and store_sales tables using SQL UNION to see all sales in one result set.

📋 What You'll Learn

Create two tables: online_sales and store_sales with columns sale_id and amount

Insert exact sales data into both tables

Write a SQL query using UNION to combine sales from both tables

Order the combined results by sale_id

💡 Why This Matters

🌍 Real World

Combining sales data from different sources helps businesses get a complete view of their transactions.

💼 Career

Database professionals often combine data from multiple tables or databases to create reports and insights.

1

Create the sales tables

Create two tables called online_sales and store_sales. Each table should have two columns: sale_id as an integer and amount as a decimal number.

MySQL

-- Create the online_sales and store_sales tables
-- Your code here

Need a hint?

Use CREATE TABLE statements with the exact column names sale_id and amount.

2

Insert sales data

Insert these exact rows into online_sales: (1, 15.50), (2, 23.75). Insert these exact rows into store_sales: (3, 10.00), (4, 5.25).

MySQL

CREATE TABLE online_sales (sale_id INT, amount DECIMAL(10,2));
CREATE TABLE store_sales (sale_id INT, amount DECIMAL(10,2));
-- Insert sales data into online_sales and store_sales
-- Your code here

Need a hint?

Use INSERT INTO with the exact values for each table.

3

Combine sales with UNION

Write a SQL query that uses UNION to combine all rows from online_sales and store_sales. Select sale_id and amount from both tables.

MySQL

CREATE TABLE online_sales (sale_id INT, amount DECIMAL(10,2));
CREATE TABLE store_sales (sale_id INT, amount DECIMAL(10,2));
INSERT INTO online_sales VALUES (1, 15.50), (2, 23.75);
INSERT INTO store_sales VALUES (3, 10.00), (4, 5.25);
-- Write a UNION query to combine sales
-- Your code here

Need a hint?

Use SELECT from each table and combine with UNION.

4

Order the combined results

Add an ORDER BY sale_id clause at the end of your UNION query to sort all sales by sale_id.

MySQL

CREATE TABLE online_sales (sale_id INT, amount DECIMAL(10,2));
CREATE TABLE store_sales (sale_id INT, amount DECIMAL(10,2));
INSERT INTO online_sales VALUES (1, 15.50), (2, 23.75);
INSERT INTO store_sales VALUES (3, 10.00), (4, 5.25);
SELECT sale_id, amount FROM online_sales
UNION
SELECT sale_id, amount FROM store_sales
-- Add ORDER BY sale_id here
-- Your code here

Need a hint?

Place ORDER BY sale_id after the UNION query to sort results.