Ace gate test series

Question

Decompose this table in BCNF ,decomposition should be lossless and dependency preserving.

plz clarify me how to decompose to get a lossless decomposition here.

Comments

R1(AB),R2(BD),R3(ACE) why not?????

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ACE is not BCNF.

Answer 1

This table can be decomposed into BCNF as AC, CE, BD, AB . In AC, no FD is present, so it is in Bcnf form (a table with 2 attributes is always in Bcnf) in CE table, C is the superkey, in BD table, B is the superkey and in AB table, A is the superkey , and it will be dependency preserving as well as lossless decomposition.

Comments

so we will not have bcnf as well as lossless decomposition..!

Answer 2

4 tables created ..

here candidate key is AC...

so A->B fails to be in bcnf ....so we divide it in table ABD....in which B->D fails so we divide in AB and BD...

C->E again fails so we divide ....CE is table...

lastly to maintain KEYS ...we have AC...

so totals tables are

(AC)(BD)(AB)(CE)

Comments

4 tables will be created for bcnf decomposition.... AC,  AB, CE, BC..... these will be lossless as well as dependency preserving.... If it would had been asked for 2nf... Then only 3 tables will be created... AC, ABD, CE

Answer 3

4 table 

Comments

your table no 2 and 4 is same total 3 table is require.

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4^th table required for candidate key (AC)