0 votes 0 votes According to me, the answer should be option D only! please verify! Databases databases + – Utkarsh Joshi asked Oct 21, 2018 • edited Oct 21, 2018 by Utkarsh Joshi Utkarsh Joshi 760 views answer comment Share Follow See all 21 Comments See all 21 21 Comments reply Magma commented Oct 21, 2018 reply Follow Share yes with respect to me ii) and iii ) is correct 0 votes 0 votes Magma commented Oct 21, 2018 reply Follow Share because $\phi$ is proper subsets of every non empty sets 0 votes 0 votes Utkarsh Joshi commented Oct 21, 2018 reply Follow Share Magma How option 2 you are getting correct?? if s1={t1,t2} s2={t2,t3}, s3={t1,t3} etc.. its union won't be entire set. According to me only option 3 is correct so D is correct! 0 votes 0 votes Magma commented Oct 21, 2018 reply Follow Share sorry the picture that you post ...it's not clearly visible so I didn't notice this part : "example s1={t1,t2} " 0 votes 0 votes Magma commented Oct 21, 2018 reply Follow Share but there also be a case when s1={t1,t2} s2={t3,t4}, s3={t5,t6} ...... Sn/2 = (tn-1 , tn) then it's hold ii and iii right ??? 0 votes 0 votes Utkarsh Joshi commented Oct 21, 2018 reply Follow Share okay idk why pic is blur 0 votes 0 votes Utkarsh Joshi commented Oct 21, 2018 reply Follow Share Magma yes in some cases it will hold but not all. 0 votes 0 votes Magma commented Oct 21, 2018 reply Follow Share Utkarsh Joshi yeah right s1={t1,t2} s2={t2,t3}, s3={t1,t3} and In this case option i) is also hold :p 0 votes 0 votes Utkarsh Joshi commented Oct 21, 2018 reply Follow Share yes thats why i marked none of above! ;p 0 votes 0 votes Shaik Masthan commented Oct 21, 2018 reply Follow Share i and iii always right, but ii is sometimes right 0 votes 0 votes Magma commented Oct 21, 2018 reply Follow Share s1={t1,t2} s2={t3,t4}, s3={t5,t6} ...... Sn/2 = {tn-1 , tn} Shaik Masthan In this case i is not right 0 votes 0 votes Utkarsh Joshi commented Oct 21, 2018 reply Follow Share 1 will be false when all subsets are disjoint. In that case union will be =R 0 votes 0 votes Utkarsh Joshi commented Oct 21, 2018 reply Follow Share Only 3 will be always correct acc to me 0 votes 0 votes Shaik Masthan commented Oct 21, 2018 reply Follow Share brother, every set is subset to itself... It is trivial 0 votes 0 votes Magma commented Oct 21, 2018 reply Follow Share Shaik Masthan brother it's not a subset $\subset$ ---- > it's proper subset if it's given " $\subseteq$ " instead of " $\subset$ " then (i) is always true 2 votes 2 votes Somoshree Datta 5 commented Oct 21, 2018 reply Follow Share Answer should option (c) since all the three cases are being satisfied by taking certain subsets for a relation. Here the question didnt ask for the statements that are always true..they just asked for which of the statements are true..so i think if u can give atleast one example for each of the three cases, then that statement becomes true..may not be true always..but surely it is true for certain examples. 0 votes 0 votes Shaik Masthan commented Oct 22, 2018 reply Follow Share @Magma YES, YOU ARE RIGHT !.... thanks for correcting me @Somoshree Datta 5 no need to match the answers.... we have to go as per the concept. 0 votes 0 votes Somoshree Datta 5 commented Oct 22, 2018 reply Follow Share @Shaik Masthan But the first option is also getting satisfied for the following example: Let R contain six tuples 1,2,3,4,5,6. Now let the 3 subsets be : S1={1,2} S2={2,3} S3={3,4} So here if we do S1US2US3={1,2,3,4} which is clearly a proper subset of the relation R. So how can u say that option i is false? 0 votes 0 votes Shaik Masthan commented Oct 22, 2018 reply Follow Share for showing it is false, just one counter example sufficient. but for showing it is true, just one example is not sufficient, it should satisfy all the cases 0 votes 0 votes Somoshree Datta 5 commented Oct 22, 2018 reply Follow Share ok..got it.. So only option iii should be right in that case..right? 0 votes 0 votes Shaik Masthan commented Oct 22, 2018 reply Follow Share yes 0 votes 0 votes Please log in or register to add a comment.