All our hosting plans include MySQL database by default, our Linux servers also have PostgreSQL and Microsoft SQL Server is available as an optional extra on our Windows servers.
Just like our website and database limits we do not limit the number of databases you can create and the only limit for MySQL and PostgreSQL are the hosting plans space and bandwidth limits.
With MSSQL however you are limited by the amount of add-on MSSQL space purchased, each MSSQL add-on comes with 250MB of space and you can purchase additional instances in 250MB space increments however again we don't limit the number of databases you can create.