1 votes 1 votes A system where commutativity is considered different, in how many ways the join of n relations r1,r2,…, rn can be taken? 1. (2n−2)!/(n−1)! 2. (2n−2)!/n!(n−1)! 3. (2n−1)!/n!(n−1)! 4. None Databases nptel-quiz databases + – gulsanchouhan asked Aug 26, 2017 gulsanchouhan 420 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes for n=2 ... 1.r1 join r2 and r2 join r1 ....option 2 and 3 are eliminated .... now for n=3(it is 12) ... r1Jr2Jr3{can be arranged in 6 way and for each arrangement(2way for associativity)... similarly for n=4 (i.e 120).. i think 1st is the option ?????? hs_yadav answered Sep 4, 2017 hs_yadav comment Share Follow See all 0 reply Please log in or register to add a comment.