Yesterday in technical interviewer asked one intertestin question in RDMS table weather primary key is editable or not, your input please on this question.

Interviewer asked me this interesting question in SQL server section, still I am not able to understand and find solution.

I requested interviewer to elaborate more on this question then he replied is there any constraint to add primary key in SQL table with sequence or not. 

These are some series of interesting questions interviewer asked me in last week, I was confused with this question request community friends for proper answer with difference between auto increment and squence.