SQL Server Security Mechanism

In the past, Oracle was used more often. When SQL Server was used, I found a problem. Here I will discuss it with you.

In Oracle, a database includes users and roles, so each database is independent of each other. However, it is different in SQL Server. SQL Server introduces the login concept. login is for SQL Server services, but not for databases, such:

It shows how to install multiple databases on one server. (Ignore the NT authentication method) as shown in the figure, login conflicts may occur when multiple databases are deployed on SQL Server, that is, when different applications create login, when the login name is repeated, a conflict occurs.

Of course, when a B/S system is implemented, the user will not establish a login, and such a problem cannot occur. However, this situation must be considered in the C/S system.

At present, there is no good way to tell the user: it is best to deploy only one database on sqlserver.

Which of the following is a better solution?