Overview of SQL UNION

This article will provide a deep dive into the SQL UNION operator, describing its many uses along with examples and explore some common questions like the differences between UNION vs UNION ALL.

To address real-world data requirements, we may need to combine result sets from multiple data sources so that we could do data analysis or create new datasets. The datasets may be identical but there are chances that they reference different tables. Is there a way to combine the data in a single query? Are Set Operators a viable option? Let’s get started and see how some of the existing operators can be used to help us address these common challenges.

In this article, we’ll review:

1. What a Set operator is
2. UNION vs UNION all and how they work
3. Discuss the rules for using UNION vs UNION ALL
4. SQL Operator Syntax
5. How to use simple SQL UNION clause in the select statement
6. How to use SQL UNION with the queries that have the WHERE clause
7. How to use the SELECT INTO clause with UNION
8. How to use SQL UNION with the queries that have a WHERE clause and order by clause
9. How to use SQL UNION and SQL Pivot
10. How to use SQL UNION with GROUP and HAVING clauses

 

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SQL Union