1 votes 1 votes $R(X,Y,Z,W) is\ decomposed\ into \\ R_1(X,Y)\\ R_2(Y,Z)\\ R_3(Y,W).\\The\ FDs\ are\ :\\ X -> Y,\\ Z->Y,\\ Y->W \\ Find\ whether\ the\ decomposition\ is\ lossless\ or\ lossy\ ?$ Databases databases decomposition lossless-join + – Tuhin Dutta asked Dec 8, 2017 Tuhin Dutta 614 views answer comment Share Follow See all 4 Comments See all 4 4 Comments reply joshi_nitish commented Dec 8, 2017 reply Follow Share it is lossy. 3 votes 3 votes Ashwin Kulkarni commented Dec 8, 2017 reply Follow Share Lossy and FD preserving 2 votes 2 votes hs_yadav commented Dec 8, 2017 reply Follow Share R1&R3 will be combined ...but for R2 Let consider this example:- X Y Z W 2 2 3 6 3 2 4 7 1 2 2 8 Now consider decomposition R2:- Y Z 2 3 2 4 2 2 R1R3=R' X Y W 2 2 6 3 2 7 1 2 8 now th3 natural join of R' and R2 wil give following relation:- X Y Z W 9 touples...not like the old table therefor Lossy decomposition 2 votes 2 votes Shamim Ahmed commented Dec 25, 2018 reply Follow Share Lossy and FD preservi 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes LOSSY (X,Y) AND (Y.Z) HAS COMMON ATTRIBUTE Y WHICH IS NOT A PRIMARY KEY OF ANY OF THE TABLE(R1 OR R2). Priyanka Agarwal answered Dec 8, 2017 Priyanka Agarwal comment Share Follow See all 0 reply Please log in or register to add a comment.
1 votes 1 votes lossy.. abhishekmehta4u answered Mar 29, 2018 abhishekmehta4u comment Share Follow See all 0 reply Please log in or register to add a comment.