SQL Union is a powerful tool that allows you to combine the results of two or more SELECT statements into a single result set. This can be incredibly useful when you need to combine data from multiple tables or databases, or when you need to perform complex queries that require data from multiple sources.
In this tutorial, we will provide a brief overview of SQL Union and show you how to use it in your own SQL queries.
SQL Union is a set operator that combines the results of two or more SELECT statements into a single result set. The result set returned by a Union operation contains all the rows that are returned by each SELECT statement, with duplicates removed.
It is important to note that the columns in each SELECT statement must match in terms of data type and order. If they do not, you will receive an error message.
Using SQL Union is relatively straightforward. To use it, you simply need to include the Union operator between two or more SELECT statements. Here is an example:
SELECT column1, column2 FROM table1 UNION SELECT column1, column2 FROM table2;
In this example, we are selecting the columns "column1" and "column2" from two different tables, "table1" and "table2". The Union operator is used to combine the results of these two SELECT statements into a single result set.
It is important to note that the Union operator removes duplicates from the result set. If you want to include duplicates, you can use the Union All operator instead:
SELECT column1, column2 FROM table1 UNION ALL SELECT column1, column2 FROM table2;
In this example, the Union All operator is used to include duplicates in the result set.
SQL Union is a powerful tool that allows you to combine the results of two or more SELECT statements into a single result set. It is incredibly useful when you need to combine data from multiple tables or databases, or when you need to perform complex queries that require data from multiple sources.
If you are new to SQL, we recommend that you spend some time learning the basics before diving into Union operations. Once you have a solid understanding of SQL, however, Union can be an incredibly powerful tool that can help you to solve complex data problems.