Normalization question

[indiocolifa]

I've the following table to normalize:

R(a,b,c,d)

The functional dependencies are:

a ---> b
b ---> a
a,c ---> d
b,c ---> d

There are no keys defined.

How I can identify the candidate keys on the relation from the fds? My book has examples always with defined keys, but not like this.

Thank you.

[Dr John]

homework, eh

cos that's the only place you'd get a question like this on functional dependencies.

When there is more than one candidate key, the only thing that a candidate key can be dependant on is another candidate key. Find the attribute(s) upon which all other attributes are dependant.
(eg unique ID and unique social security number can both be candidate keys for an employee's name, address, age, shoesize, etc)

I'm a little bit out of practice at these sort of problems now, so can't take you through the steps, but hey, I always .did my own homework...

[r937]

cos that's the only place you'd get a question like this

quoted for truth