PostgreSQL SyntaxLesson 36Free preview

PostgreSQL UNION

This lesson is part of PostgreSQL · All levels

Summary

UNION brings together the results of two or more SELECT queries into one combined row list. The main requirement is the same number of columns and the same data type as the interquery. Use UNION if you only want unique results, or UNION ALL if duplication is allowed and performance is preferred.

Key points

Union combines the results of two queries with the same number of columns.
Union deleted the duplicate, Union All maintained it.
The column name follows the first query.
Filtering is done individually through WHERE before merging.

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