# Return to Question

3 improved language

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But I don't get it... why? Why not only {EF}.. it got less attributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other attributes, why it'sis it not a key?

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But I don't get it... why? Why not only {EF}.. it got less attributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other attributes, why it's not a key?

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But I don't get it... why? Why not only {EF}.. it got less attributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other attributes, why is it not a key?

2 improved language

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But i dontI don't get it... why? Why not only {EF}.. it got less atributesattributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other atributesattributes, why itsit's not a key?

thanks in advance.

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But i dont get it... why? Why not only {EF}.. it got less atributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other atributes, why its not a key?

thanks in advance.

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But I don't get it... why? Why not only {EF}.. it got less attributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other attributes, why it's not a key?

1

# Keys of a relation

I got relation:

R = { (ABCDEF) , (A B F -> C, B C -> F, F -> A, F -> B, D E -> E, E -> D)}

keys of this relation are:

{BCE}, {EF}

But i dont get it... why? Why not only {EF}.. it got less atributes than {BCE}..

Another example, relation:

R2 = {(ABCDEF), (A -> B C , B -> D , E -> F)}

and the key is:

{AE}

why only one? Why not:

{AE}, {ABE}

ABE also determines all other atributes, why its not a key?

thanks in advance.