Why UNION combining result sets in SQL? - Purpose & Use Cases

The Big Idea

What if you could combine multiple lists into one with a single simple command?

The Scenario

Imagine you have two separate lists of customer orders from two different stores saved in separate files. You want to see all orders together in one list to understand total sales.

The Problem

Manually copying and pasting orders from one list to another is slow and mistakes happen easily. You might miss some orders or duplicate others, making your final list unreliable.

The Solution

The UNION command in SQL lets you combine these two lists into one clean, unified list automatically. It saves time and ensures no duplicates sneak in unless you want them.

Before vs After

✗ Before

Copy orders from Store1 list
Paste into Master list
Copy orders from Store2 list
Paste into Master list

✓ After

SELECT * FROM Store1Orders
UNION
SELECT * FROM Store2Orders

What It Enables

With UNION, you can easily merge multiple sets of data into one complete view for better decisions.

Real Life Example

A business owner combines sales data from multiple branches to see total revenue without errors or extra work.

Key Takeaways

Manually merging data is slow and error-prone.

UNION combines multiple result sets into one automatically.

This makes data analysis faster and more reliable.