SET NOCOUNT ON;

DECLARE @user_name    SYSNAME
        , @login_name SYSNAME;

SELECT @user_name = '',
       @login_name = ''

SELECT '
    USE ' + QUOTENAME(NAME) + ';
	BEGIN TRY
    CREATE USER ' + QUOTENAME(@user_name)
       + ' FOR LOGIN ' + QUOTENAME(@login_name)
       + ' WITH DEFAULT_SCHEMA=[dbo];
	END TRY
	BEGIN CATCH
		/* User exists - do nothing */
	END CATCH
    EXEC sys.sp_addrolemember
      ''db_datareader'',
      ' + QUOTENAME(@user_name) + ';

    EXEC sys.sp_addrolemember
      ''db_datawriter'',
      '
       + QUOTENAME(@user_name) + ';
GO
'
FROM   sys.databases
WHERE  database_id > 4
       AND state_desc = 'ONLINE'
       -- AND name LIKE '%...%'