Some Confusion in 2NF(Normalization)

I have some confusion while normalizing in 2NF

Consider set of FD's

FD1   ABD->C
FD2   BC->D
FD3   CD->E

H开发者_Python百科ere the keys are ABD,ABC

Prime Attributes-A,B,C,D

Non-Prime Attribute-E

2NF-For a relation to be in 2NF,Non Prime Attribute should be fully functional dependent on key.

Will the FD3 violates 2NF? Is CD proper subset of key?One more thing I want to ask how do we decide which FD to put in separate relation when it violates 2NF?Please help

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CD is not a proper subset of a key but BC is.

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Well in FD3, we have given CD->E WHERE E is non prime attribute and CD is the subset of prime key as C and D both are the part of primary key and we will not accept those in 2NF which are the subsets and the rest of the two(i.e. FD1 AND FD2) they are in 2NF because there RHS has prime attribute whch is accepted in 2NF. So FD3 doesn't violates 2NF. CD is proper subset.