How Impersonation Works
Here’s an illustration of how database user impersonation works:
In the above illustration, Jane Smith (MyCo\jsmith) is a West Coast sales representative and Henry Wilson (MyCo\hwilson) covers the East. In the SQL Server database, the account permissions for Jane's account, MyCo\jsmith, only give her access to West Coast data. Henry's account, MyCo\hwilson, can only access data for the East Coast.
A view has been created that displays data for the entire country. It has a live connection to a SQL Server database. Both users sign in to Tableau Server and click the view. Tableau Server connects to SQL Server using a database account with IMPERSONATE permission for each user's database account. This account acts on behalf of each user's database account.
When the view displays, it is restricted by each user's individual database permissions: Jane sees only the West Coast sales data, Henry sees only the East Coast data.