Difference Between UNION and UNION ALL in SQL

When comparing UNION with UNION ALL, there is a significant difference:

  • UNION returns only unique records, while UNION ALL returns all records, including duplicates.
  • UNION performs additional processing to identify and eliminate duplicate rows, which can make it slower compared to UNION ALL.

In this article, we will look at the differences between UNION and UNION ALL in SQL with multiple examples.