SQL UNION Operator

UNION operator is used to get the combine results of two or more tables.
every select statement of tables must have same fields name with same data type and same order.
it used to get unique value from tables.

For SELECT Statement

Syntax:-

SELECT column_name(s) 
FROM table_name1

UNION

SELECT column_name(s) 
FROM table_name2

Example:- Suppose we have two table employees and users.

employees Table:-

+----+------------+-----------+----------------+-----------+
| id | first_name | last_name | email          | country   |
+----+------------+-----------+----------------+-----------+
|  1 | John       | Tailor    | john@abc.com   | USA       |
|  2 | Rom        | Tailor    | rom@abc.com    | USA       |
|  3 | Andrew     | Symonds   | andrew@abc.com | Australia |
|  4 | Miacle     | Tailor    | miacle@abc.com | Australia |
|  5 | Sachin     | Tendulkar | sachin@abc.com | India     |
|  6 | Virat      | Kohli     | virat@abc.com  | India     |
|  7 | rohit      | NULL      | rohit@abc.com  | India     |

users table:-

+----+------------+-----------+----------------+---------+
| id | first_name | last_name | email          | country |
+----+------------+-----------+----------------+---------+
|  1 | Ramesh     | Kumar     | ramesh@abc.com | India   |
|  2 | Suresh     | Kumar     | suresh@abc.com | India   |
|  3 | Anna       | Symonds   | anna@abc.com   | USA     |
+----+------------+-----------+----------------+---------+
3 rows in set (0.00 sec)

Find the country name which has unique name.

Query:-

SELECT country FROM employees
UNION
SELECT country FROM users

Output:-

+-----------+
| country   |
+-----------+
| USA       |
| Australia |
| India     |
+-----------+
3 rows in set (0.00 sec)

SQL UNION Operator – Interview Questions

SQL UNION Operator – Objective Questions (MCQs)

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