data-konzept

'What are Orphaned Users

“Orphaned Users” is a common issue in SQL Server where a Database User is no longer associated with its relevant Server Login.

This often happens when the Server Login is deleted (even if  it’s recreated later), or when the database is moved or restored to a different SQL Server.
You can find some more info on it in this article from Microsoft.

The symptoms that you can expect from such a scenario is inability to use such database users.
Specifically, using the login to connect to the database that it’s supposed to be mapped to. It just doesn’t work.
You’ll receive the following error:

Login failed for user ‘MyUser’. (Microsoft SQL Server, Error: 18456)

The Login could exist on the server level.
The User also exists within the relevant database.
But it doesn’t work because the SID that the database user is mapped to, is different from the SID of the actual Server Login.

This is the real problem, because Users are mapped to their Logins by their SID, not by their names.
And every time you create a new Login, it receives a new, random SID.'...

http://www.sqlservercentral.com/blogs/eitan-blumin/2018/01/03/how-to-fix-orphaned-users-easily/?utm_source=SSC&utm_medium=pubemail