Orphaned users

Servers have Logins, and databases have Users.

A Login and a User account are linked, sharing the same name and the same SID. Naturally, for each Login there can be many User accounts – one in each database.

Now, if you backup a database on one server and restore it onto another server. It may contain Users within that database, that do not have a corresponding Login on the second server.

Execute this command (against each user database) to list any orphaned Users …

SELECT 	DP.type_desc,
        DP.SID,
        DP.[name] UserName
FROM [sys].[database_principals] DP
LEFT JOIN [sys].[server_principals] SP
       ON DP.SID = SP.SID
WHERE SP.SID IS NULL
AND DP.authentication_type_desc = 'INSTANCE';

To fix this you can either remove the orphaned user account or create a matching login. Removing a user account is tricky to script as you need to remove individual attributes first.

Creating a login depends on the type, SQL or Windows. For SQL logins paste the name, SID, and password* into this command and execute it.

USE [master]
GO
CREATE LOGIN [SomeLogin]
WITH PASSWORD = 'SomePassword',  
SID = 0xSomeSid;

(*If you do not know the SQL login password that was used on the old server then create a new one. They are not linked)

To create a Windows login use this command …

USE [master]
GO
CREATE LOGIN [SomeDomain\SomeLogin] 
FROM WINDOWS 
WITH DEFAULT_DATABASE = [master];