Which MariaDB operator is used to combine the result sets of two or more SELECT statements?

MariaDB is a community-developed, commercially supported fork of the MySQL relational database management system, intended to remain free and open-source software under the GNU General Public License.
The biggest advantage of MariaDB over MySQL is its speed and performance. When it comes to replication and performing queries, MariaDB is faster than MySQL. In addition, MariaDB also easily supports a high concurrent number of connections without much performance degradation.