This is personal study note Copyright and original reference: https://www.youtube.com/watch?v=yCbJ1D1Ylik&list=PLuHgQVnccGMAG1O1BRZCT3wkD_aPmPylq&index=2 ================================================================================ duplication ================================================================================ Add comment table and get another duplicate ================================================================================ By splitting table, remove duplicate ================================================================================ Split into author and profile