MySQL is one of the most popular open source relational databases. There exists an external MySQL client package, which can be used with vibe.d.
The central website for MySQL is http://dev.mysql.com/downloads/. You can download precompiled binaries for many platforms, including a Windows installer.
All Linux distributions offer a MySQL package, which you can use. Let's take a look at how you can install MySQL on a few other operating systems:
$ sudo apt-get install mysql-server
$ sudo yum install mysql
$ sudo dnf install mysql