https://naiwaen.debuggingsoft.com/2021/06/db2-%e0%b8%97%e0%b8%b3%e0%b9%84%e0%b8%a1%e0%b8%95%e0%b9%89%e0%b8%ad%e0%b8%87%e0%b8%a5%e0%b8%87-dbms-%e0%b9%81%e0%b8%a5%e0%b8%b0-%e0%b8%aa%e0%b8%a3%e0%b9%89%e0%b8%b2%e0%b8%87-db-%e0%b9%83%e0%b8%ab/