The H2 database is configured to run as an embedded database and though you can enable the web console for human interaction with the DB while Mango is running (use the db.web.start property in your env.properties), I don't think it's serving database connections, so no.

It probably is possible to make happen, but it may involve performance compromises with the embedded mode of the database.

I would advise converting your system to use MySQL if you intend to have other clients for the database server directly (as opposed to querying Mango through the UI or API)

Now it works, thanks.
But I insert the absolute path of the file system. I would be interested to know if I can query the DB on localhost or from an external server.

I would guess the icon flashing was the timeout for the connection and took more waiting or there was an error in the page you could see in your developer tools.

My guess from the configuration you've posted is that you need to have the MySQL port in the connection string, and if you're using the default MySQL port, that should be,

jdbc:mysql://localhost:3306/specificDatabase

I can guess from your select statement that you intend to be getting data out of Mango's database. Are you using MySQL (where H2 would be the default database)? You can find the appropriate connection string for your database type in your env.properties file, simply replace ${ma.home} with you /path/to/Mango

Try the settings (if you are trying to query the default H2 database),

Driver class: org.h2.Driver //this is in the contextual help
Connection string: /path/to/Mango/databases/mah2
Username:
Password: