![]() ![]() In other words, join appends the result sets horizontally while union appends the result set vertically. The join such as INNER JOIN or LEFT JOIN combines columns from two tables while the UNION combines rows from two queries. In other words, the UNION operator removes the duplicate rows while the UNION ALL operator includes the duplicate rows in the final result set. However, if you want to retain the duplicate rows, you need to specify the ALL keyword is explicitly as shown below: query_1 UNION ALLīy default, the UNION operator removes all duplicate rows from the result sets. The following Venn diagram illustrates how the result set of the T1 table unions with the result set of the T2 table: UNION vs. The data types of the corresponding columns must be the same or compatible.The number and the order of the columns must be the same in both queries.The following are requirements for the queries in the syntax above: The following illustrates the syntax of the SQL Server UNION: query_1Ĭode language: SQL (Structured Query Language) ( sql ) SQL Server UNION is one of the set operations that allow you to combine results of two SELECT statements into a single result set which includes all the rows that belong to the SELECT statements in the union. Introduction to SQL Server UNION operator ![]() Summary: in this tutorial, you will learn how to use the SQL Server UNION to combine the results of two or more queries into a single result set.
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