database

Question

If table is has only two  coloumns,in which normal form would it be? 

Answer 1

2 columns means 2 attributes , A relation R with two attributes then R will always  in BCNF

let R (A,B)

1) A → B  ⇒ BCNF (becoz A⁺={A,B}, A is super key )

2) B → A   ⇒ BCNF (becoz B⁺={A,B}, B is super key )

3) A → B ,B → A  ⇒ BCNF (here A and B are super key )

4) NO non trivial dependency   ⇒ BCNF (becoz trivial FD's are always implied)

Comments

A->B AND B->A BOTH WILL NOT BE TRUE AT SAME TIME

---

actually here i m considering all possible functional dependency.

Answer 2

2 columns means 2 attributes.   A relation with 2 attributes  is always BCNF.  

Bcz for testing conditions  of BCNF says  that left hand side should be a candidate  key of every relation of the relational table .So this condition  will always  satisfy in this case.

And when bigger one satisfies  , we will never go for checking  smaller one . They will always satisfied.

Answer 3

"A relation with 2 attributes will always be in BCNF "

Answer 4

IF RELATION CONSIST OF ONLY TWO COLUMNS(ATTRIBUTE) SAY P & Q THEN 'PQ' TOGETHER WILL HAVE DISTINCT VALUES FOR EACH TUPLE .

E.G

ROLL NO.(P)	NAME (Q)
1	NIRAJ
2	NIRAJ
3	SURAJ

EVEN THOUGH COLUMN CAN HAVE DUPLICATES BUT TOGETHER THEY MUST BE UNIQUE.

I.E EITHER P->Q OR Q->P WILL MUST BE VALID (IN GIVEN EXAMPLE P->Q). WHICH SATISFY THE CONDITION OF BCNF THAT LEFT HAND SIDE SHOULD BE A SUPERKEY.

SINCE ONLY TWO NON TRIVIAL RELATIONS I.E P->Q AND Q->P ARE POSSIBLE WITH TWO ATTRIBUTE .OUT OF WHICH AT LEAST ONE WILL BE TRUE . HENCE RELATION WILL ALWAYS BE IN BCNF

Answer 5

If only 2 columns are there we cannot have problems of 1,2 and 3 NF.It is always BCNF