For the limited MySQL Database allowance or usages or 10-15 database allowed to create — this a great limitation. And sometimes it’s really important to create separate MySQL database for each blogs or projects. But, in WordPress it’s not a problem — user can use Single Database and Install multiple Blogs under a MySQL Database.
A simple tricks can handle or enable this functions — when you are in config.php, don’t change anything just find $table_prefix and you will see by default it has ‘wp_’ . You can give another name such as
$table_prefix = 'wp_'; // example: 'wp2_' or 'b2' or 'mylogin_' or 'wp2'.
You don’t need to change the DB_NAME, DB_USER, DB_PASSWORD for multiple installations.A little confusion may arise when multiple installation has done – better give for blogs ‘myblogs_’, for projects ‘projects1_’ or for ‘corporate1_’. It’s simple and easy to install multiple blogs.