3 votes 3 votes A relation $R(P,Q,R,S)$ has $\{PQ, QR, RS, PS\}$ as candidate keys. The total number of superkeys possible for relation $R$ is ______ Databases tbb-dbms-2 numerical-answers databases candidate-key + – Bikram asked Aug 26, 2017 retagged Sep 17, 2020 by ajaysoni1924 Bikram 717 views answer comment Share Follow See all 4 Comments See all 4 4 Comments reply Surabhi Kadur commented Oct 15, 2017 i reshown by Surabhi Kadur Oct 15, 2017 reply Follow Share @bikram sir, shouldnt the answer be 8 ?? 0 votes 0 votes Surabhi Kadur commented Oct 15, 2017 reply Follow Share @Bikram sir, shouldnt the answer be 8 ?? 0 votes 0 votes joshi_nitish commented Oct 15, 2017 reply Follow Share yes, answer should be 8. 0 votes 0 votes AakS commented Dec 2, 2017 reply Follow Share with 4 elements i.e. {P,Q,R,S}, the number of combinations possible are 24 i.e. 16. Now from these 16 exclude o length and 1 length elements. thus 16-5 = 11. now with the length of 2 two combinations are not candidate keys i.e. PR and QS. So subtract these 2 also. Hence 11-2 i.e. 9 are the candidate keys 1 votes 1 votes Please log in or register to add a comment.
Best answer 9 votes 9 votes Number of Superkeys which are superset of PQ = 2^2 = 4 Number of Superkeys which are superset of QR = 2^2 = 4 Number of Superkeys which are superset of PS = 2^2 = 4 Number of Superkeys which are superset of RS = 2^2 = 4 Number of Superkeys which are superset of PQR = 2^1 = 2 Number of Superkeys which are superset of PQS = 2^1 =2 Number of Superkeys which are superset of PRS = 2^1 =2 Number of Superkeys which are superset of QRS = 2^1 = 2 Number of Superkeys which are superset of PQRS = 2^0 = 1 So, applying the formula of Set theory, the total number of Superkeys possible on given relation are = 4+4+4+4-2-2-2-2+1 = 9 anchitjindal07 answered Oct 17, 2017 selected Jan 19, 2019 by Shaik Masthan anchitjindal07 comment Share Follow See all 0 reply Please log in or register to add a comment.
2 votes 2 votes PQRS QRPS RSPQ PSQR PQR QRP RSP PSQ PQS QRS RSQ PSR PQ QR RS PS No need to take others as they are repeated. You can take any one of them, just ensure that you have not taken them two times. KUSHAGRA गुप्ता answered Jan 9, 2020 KUSHAGRA गुप्ता comment Share Follow See all 0 reply Please log in or register to add a comment.