Syntax
------

USE db_name

Description
-----------

The 'USE db_name' statement tells MariaDB to use the db_name database as the
default (current) database for subsequent statements. The database remains the
default until the end of the session or another USE statement is issued:

USE db1;
SELECT COUNT(*) FROM mytable;   # selects from db1.mytable
USE db2;
SELECT COUNT(*) FROM mytable;   # selects from db2.mytable

The DATABASE() function (SCHEMA() is a synonym) returns the default database.

Another way to set the default database is specifying its name at mysql
command line client startup.

URL: https://mariadb.com/kb/en/use/