0 votes 0 votes As Candidate key allow NULL value if two record have NULL value then how we identify the record uniquely. Plzz explain the concept Akash007 asked Sep 16, 2017 Akash007 1.0k views answer comment Share Follow See all 3 Comments See all 3 3 Comments reply Habibkhan commented Sep 16, 2017 reply Follow Share Look at the point 3 of ur notes.It clearly explains the picture..:) 0 votes 0 votes Akash007 commented Sep 16, 2017 reply Follow Share 3 point is for primary key. As one of the candidate is primary key. I m saying if other candidate key allow NULL and candidate key is a composite attribute and in one attribute 2 NULL are present as in image. It violates the 1 point. We can not identify record uniquely with candidate key 0 votes 0 votes rahul sharma 5 commented Sep 16, 2017 reply Follow Share If we cannot identify the records then it is not candidate key.Candidate key can be null but no two records over candidate key can have same values.But in your example two records are having same value of attributes over candidate key.In this example ABCD will be candidate key 0 votes 0 votes Please log in or register to add a comment.
0 votes 0 votes Brother modify ur point 1 as below 1. Candidate key uniquely identify the record whether it is not null & unique in row. hem chandra joshi answered Sep 16, 2017 hem chandra joshi comment Share Follow See all 0 reply Please log in or register to add a comment.