How to Combine Results Using UNION in MySQL in 2025

The growing complexity of data management requires efficient handling of databases. MySQL, a flexible and powerful database system, allows developers to perform a variety of operations seamlessly. One such operation is combining results from multiple queries using the UNION operator. In this guide, we will discuss how to use UNION in MySQL efficiently in 2025.

Understanding the UNION Operator

The UNION operator in MySQL is used to combine the results of two or more SELECT queries. Each SELECT query within the UNION must have the same number of columns in the result sets with similar data types. Using UNION, you can merge results from different tables or from various SELECT operations within the same table.

Syntax

The basic syntax for using UNION is:

SELECT column1, column2 FROM table1
UNION
SELECT column1, column2 FROM table2;

By default, UNION removes duplicate rows from the result set. If you wish to retain duplicates, use UNION ALL.

Using UNION in 2025: Best Practices

As database management evolves, here are some best practices to follow when using UNION in 2025:

1. Ensure Column Compatibility

Ensure that the SELECT statements within the UNION operation have the same number of columns and that these columns have compatible data types.

2. Optimize Query Performance

While UNION helps in combining results, it’s crucial to optimize your queries for enhanced performance. Indexing and careful query design can prevent slowdowns, especially with larger datasets.

3. Utilize UNION ALL When Necessary

Use UNION ALL when you are sure there are no duplicate records or if duplicates in the result set are acceptable. This approach can be more performant since MySQL doesn’t need to do additional work to remove duplicates.

4. Maintain Readability and Simplicity

As databases grow in size and complexity, keeping your queries readable and straightforward is key to maintenance and debugging.

Practical Example

Let’s explore a practical example combining data from two tables, employees and managers:

SELECT id, name, email FROM employees
UNION
SELECT id, name, email FROM managers;

In this example, we assume both employees and managers tables have identical columns. The UNION operation merges entries from these tables into a single query result, removing duplicates by default.

Further Reading

For those interested in more advanced uses and integration of MySQL with other technologies, here are some resources:

• Explore MySQL search techniques: mysql search
• Learn about inserting data into a MySQL table: inserting data into mysql table
• Discover how to manage MySQL queries with Node.js: node.js mysql query

Conclusion

The UNION operator is an invaluable tool in MySQL for combining query results. By understanding its functionality and following best practices, you can efficiently manage complex data operations. Stay updated with the evolving features of MySQL to ensure your skills remain relevant and robust in 2025 and beyond.