Powershell - User Mapping SQL Server 2012
Supposing your login is created
## Creating database user and assigning database role #get variables$instanceName = "yourInstance"$loginName = "testLogin"$dbUserName = "testUserName"$databasename = "tempdb"$roleName = "db_backupoperator"$server = New-Object -TypeName Microsoft.SqlServer.Management.Smo.Server -ArgumentList $instanceName#add a database mapping$database = $server.Databases[$databasename]$login = $server.Logins[$loginName]if ($database.Users[$dbUserName]){ $database.Users[$dbUserName].Drop()}$dbUser = New-Object `-TypeName Microsoft.SqlServer.Management.Smo.User `-ArgumentList $database, $dbUserName$dbUser.Login = $loginName$dbUser.Create()#assign database role for a new user$dbrole = $database.Roles[$roleName]$dbrole.AddMember($dbUserName)$dbrole.Alter