UNION ALL Join SQL

What is a UNION ALL Join?

A UNION ALL Join is a powerful technique that allows you to combine the results of two or more SELECT statements into a single result set. Unlike traditional joins, UNION ALL Join does not require matching keys or conditions between tables. Instead, it vertically stacks the results of individual queries, presenting a unified view of the data.

When to Use UNION ALL Join?

  1. Data Concatenation: Use UNION ALL Join when you want to concatenate rows from multiple tables or queries vertically. This is particularly useful when dealing with similar datasets, and you want to see them combined in a single result set.
  2. Merging Similar Structures: If you have two tables with identical structures and want to create a consolidated dataset without any conditions, UNION ALL is the way to go.
  3. Aggregating Results: When working with similar datasets and you need to aggregate information without a specific link, UNION ALL allows you to combine the results seamlessly.

Example Code:

Consider two tables, sales_january and sales_february, each containing sales data for their respective months. A UNION ALL Join can help create a unified dataset:

SELECT *
FROM sales_january
UNION ALL
SELECT *
FROM sales_february;

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