Can't create user in SQL Server Hi guys when I try to create user for my database I always encounter this kind of error. 



This is the sequence of task I done.

I manage to create new login using windows authentication of SQL then I use that login to access SQL Server again then I create my database and set the owner of that database to the login that I was created. After creating the database, I try to create new user and assign the login I use but I was halted by this error.
It is normal you cannot associate two different user to a single login for a database. You must understand the difference between a login and a user.

A login authenticate you on the server. Once you are authenticated, the login will impersonate a user to access the specified database of the connection string.

So a login can have only one user per database.

Sample : login [myDomain\myUser] has access on SqlServer. This login can have a user per database : userA for databaseA, userB for databaseB.

If you want to add an other user to the login for the same database, you have to drop the first user. Instead, you have to create a different login for the second user.

Hope this help you.