address or phone number unique naih hote hain.. Agar ek session may do trainee apas may bhai bahen hain to un dono k Address or phone number most likely same hongay.. Is lie Address or Phone number or even name bhi unique nahi hota hai.. Primary key ka sab say best tareeqa hai k ap har ek ko ID dein.. that will be completely unique. For example: student id, course id, session id, instructor id.. That will be pure unique.
yha addrees r phone number per primary key nae lgae ge kia because yae to sb k unique hoty hay r jo unique hoty hay un per he primary key lgte hay i thnk
