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Difference between UNION and UNION ALL

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Difference between UNION and UNION ALL Empty Difference between UNION and UNION ALL

Bài gửi by bryanpassman Wed Dec 07, 2022 2:03 pm

UNION and UNION ALL in SQL are used to retrieve data from two or more tables. UNION returns distinct records from both tables, while UNION ALL returns all the records from both tables. In this article, we will explore the difference between UNION and UNION ALL. UNION and UNION ALL in SQL are set operators that combine the result of two SELECT queries. Both share standard features, with one significant difference: UNION only returns a unique record, while UNION ALL returns all the records (including duplicates). This article will explore the difference between UNION and UNION ALL.
Union all vs Union SQL.

UNION in SQL combines data from the result set of two SELECT queries into a single distinct result set. The result set to produce from UNION doesn’t contain any duplicate value. UNION ALL is an extension of UNION in SQL. As the result set of UNION of two tables doesn’t contain all the records from both tables, UNION ALL comes into the picture that returns all the records from both tables (including duplicate rows also).

UNION and UNION ALL are the two most essential SQL operators used in the database for combining the result set from multiple tables. These operators allow us to use multiple SELECT queries, retrieve the desired results, and then combine them into a final output. In this article, we are going to see how they are different from each other. Before making a comparison, we will discuss in brief about these operators.

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