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I am supposed to find FDs from the given the schema =>

     Loan(ISBN:pk, copy:pk, loandate:pk, loanerNr:fk, returnDate) 
pk = primary key fk = foreign key

Lets say that this is for a library DB-system that keeps the records of books loaned out. Also the returnDate attribute can be nill. I've comed to these FDs =>

LoanerNr, ISBN -> copy, loanDate                  
    loanDate, copy, loanerNr -> returnDate

The thing is that I'm not entirly sure if my FDs are all of the schema, and if they are right. As right now, they seems logical to me, but some input from outside would be very helpfull.

John Smith
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1 Answers1

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Attributes that constitute the primary key should determine all other attributes, i.e., loanDate, copy, ISBN -> loanerNr, returnDate

I would also expect that every person can borrow only one copy of a certain book on a given date, so loanDate, ISBN, loanerNr -> copy.

Alexander Serebrenik
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