I am new to SQL Server authentication methodologies. I am trying to learn to create a read-only user who can access Azure SQL data from Power BI. I have followed the steps and created a login and user as suggested in this post. I am able to login to the database using 'login' and password as suggested here.
My concern is, as I created the user and assigned him the role of the 'db_datareader'; how does this guarantee that I can't modify something in another database(as there can be multiple user associated with login with a different role)? Is there any way I can directly login to the database using username?