SQL UNION Operator

The SQL UNION operator is used to combine the result sets of two or more SELECT queries into a single output. It removes duplicate rows and returns only unique records from all combined queries.

• UNION ALL includes all rows, even duplicates.
• Queries must have matching columns and data types.
• Helpful for combining data from different sources.

Example: First, we create a demo SQL database and tables, on which we will use the UNION Operator command.

Query:

SELECT city FROM Table1
UNION
SELECT city FROM Table2;

Output:

Syntax:

SELECT column_name FROM table1
UNION
SELECT column_name FROM table2;

Examples of SQL UNION

Let's look at an example of UNION operator in SQL to understand it better. Let's create two tables "Emp1" and "Emp2";

Example: SQL UNION Operator

 In this example, we find the countries (only unique values) from both the "Table1" and the "Table2" tables: 

Query:

SELECT Country FROM Emp1
UNION
SELECT Country FROM Emp2
ORDER BY Country;

Output:

Note: The UNION operator combines the results of two queries and removes duplicate rows, while UNION ALL includes all rows from both queries without eliminating duplicates.