PostgreSQL Union is used to combine the result sets of two or more queries into a single result set. The Union operator removes duplicate rows from the results. The Union ALL operator includes all rows, including duplicates.PostgreSQL UNION and UNION ALL are used to combine the results of two or more queries into a single result. UNION will remove duplicate rows, while UNION ALL will not. Both operators have the same precedence, so they can be used interchangeably.PostgreSQL Union is used to combine the results of two or more queries into a single result. It removes duplicate rows between the various SELECT statements. Union ALL, on the other hand, will not remove duplicate rows. It will return all rows, including duplicates.PostgreSQL Union is a command used to combine the data of two or more tables into a single table. The data from each table is retrieved in a separate result set and then combined into a single result set, which is then returned to the user. PostgreSQL Union ALL is similar to Union, except that it does not remove duplicate rows.