1 1 vote which of the following is inccorect for the meaning of null values? A) value unknown B) value exist but not available C) attribute does not apply to this tupple D) none Databases + – Ankita Shingala 1.0k views answer comment Share Follow Print See 1 comment 1 1 comment reply sudsho commented Dec 26, 2016 reply Follow flag edit ur question..there is nthing!! 0 0 replyShare Please log in or register to add a comment.
Best answer 1 1 vote I think option d is correct because rest of options are releted to null value. . Deepak Yadav answered Dec 31, 2016 • selected Jan 1, 2017 by Arjun Deepak Yadav comment Share Follow 0 reply Please log in or register to add a comment.
2 2 votes NULL means its value doesnt exist in the present database u r working...so for u ,it's unknown....it's possible that it could exist somewhere but u dont know this...so option A is more suitable here.... sudsho answered Dec 26, 2016 • edited Dec 31, 2016 by sudsho sudsho comment Share Follow See all 6 Comments 6 6 Comments reply Show 3 previous comments Ankita Shingala commented Dec 26, 2016 reply Follow flag there is one more doubt if you don't mind here D is not there in relation R(A,B,C) so can we write FD :{AC --> B, A --> B}? and if we can then relation can't be in 2NF due to A -->B . what should be your answer? 0 0 replyShare sudsho commented Dec 26, 2016 reply Follow flag if we assume that there was no D at all anywhere, then candidate key={AC}..means partial dependency in A->B..so highest normal form possible is 1NF only.. yes u r correct.. 1 1 replyShare vishwa ratna commented Dec 26, 2016 reply Follow flag NULL values represent missing unknown data. Missing and Unknown not just missing, so D is correct. Ref: http://www.w3schools.com/sql/sql_null_values.asp 1 1 replyShare Please log in or register to add a comment.
