functional dependencies of a table having independent attributes

Question

i have doubt about independent attributes(like constant column) in a table. what should be the primary key and fds for the following example:

let a,b,c,d,e are the attributes and a,b,c uniquely identifies a row and d,e are the independent columns. then what should be the key attributes and what are the fds

Answer 1

let a,b,c,d,e are the attributes and a,b,c uniquely identifies a row and d,e are the independent columns. then what should be the key attributes and what are the fds

If ABC uniquely identifies a row, and if no subset of ABC uniquely identifies a row, then ABC is an irreducible superkey, also known as a candidate key. Assuming that ABC is the only candidate key, and assuming that ABC is also the only determinant, then these are the FDs.

• ABC->D
• ABC->E

ABC->ABC is a trivial dependency. Trivial dependencies are usually omitted.

What does assuming that ABC is the only determinant mean? It means that you don't have any other unexpressed FDs, like D->E, or AB->D, or D->A.