https://naiwaen.debuggingsoft.com/2013/10/sql-server-select-%e0%b9%81%e0%b8%9b%e0%b8%a5%e0%b8%87-column-%e0%b8%97%e0%b8%b5%e0%b9%88%e0%b9%80%e0%b8%9b%e0%b9%87%e0%b8%99-null-%e0%b9%83%e0%b8%ab%e0%b9%89%e0%b9%80%e0%b8%9b%e0%b9%87%e0%b8%99-0/