1 votes 1 votes A primary key for an entity is : a candidate key any attribute a unique attribute a superkey Databases ugcnetcse-dec2007-paper2 + – go_editor asked Mar 28, 2020 edited Jun 11, 2020 by soujanyareddy13 go_editor 779 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Option B) is surely wrong. Option D) you can discard, because in the option candidate keys is there, which is a minimal set of super key.(https://dba.stackexchange.com/questions/71924/what-is-the-difference-between-primary-key-and-super-key-in-dbms) Now in option (A) and (C), I will choose Option A, because one of the most important properties of Primary key is that it should not have NULL value. But in Option C it can not be guarantee. Hence I will choose Option (A) as answer. The primary key of a relation is a candidate key especially selected to be the key for the relation. In other words, it is a choice, and there can be only one candidate key designated to be the primary key. Mohit Kumar 6 answered May 5, 2020 Mohit Kumar 6 comment Share Follow See all 0 reply Please log in or register to add a comment.