Hacker News new | comments | show | ask | jobs | submit login

then what is the point of ever having a unique constraint

In case of something that's not a primary key, you can just get rid of it in the future. While technically it is possible to change the PK, it's way too much pain compared to having a synthetic one.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact