Article Summary
The SQL UNION operator combines results from two or more SELECT queries into a single result set, automatically removing duplicates unless UNION ALL is used. This article covers UNION syntax, UNION ALL, ordering results, column renaming, and data type conversion with CAST and CONVERT. You'll gain a clear, practical understanding of when and how to use UNION effectively.
SQL (Structured Query Language) is an industry-standard programming language for managing data in structured, relational databases. This flexible and versatile language operates by executing a series of statements that return the requested data from the database. SQL statements consist of strings of clauses that refine the search, and operators that specify how to manipulate the resulting data in a relational database. The SQL UNION operator is one of these—and it might be one of the most underused operators in SQL.
As the name implies, the UNION operator combines the result set of two or more SQL SELECT statements— the basic statement that finds and identifies data sets for all kinds of SQL operations. However, other well-structured query statements can perform the functionality of the UNION operator as well, so some database administrators and programmers consider it to be a little sloppy.
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Frequently Asked Questions
The SQL UNION operator combines the result sets from multiple separate database tables. Here’s how to use UNION to join multiple data sets in a single result. This guide provides structured insights, proven methodologies, and actionable execution steps for modern professionals.
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