Andyk

 Profile Answers by Andyk 

• Dec 15th, 2005

 

Hi

FIrst Normal form : Attribute should be atomic.

Second Normal Form : Non-Key attribute should be fully functionally dependent on key Attribute.

Third normal Form : There is no transitivity dependency between attribute. Suppose 'y' is dependent on 'x' i.e.  x->y and 'z' is dependent on 'y' i.e. y->z this is transitivity dependency So we can split table on to two tables os that result will be x->z.

Forth Normal Form : A determinant is any attribute (simple or composite) on which some other attribute is fully functionally dependent.

A relation is in BCNF is, and only if, every determinant is a candidate key.

ejaita

• Feb 12th, 2006

 

the diffrence between the normal forms

zukisani zaula

• Sep 27th, 2006

 

1)concept of funtional dependencies?

2)partial and full functional dependencies?

3)anomalies in unstructured relatioins ?

4)firt ,second and third normal forms ?

sravan kumar

• Dec 8th, 2006

 

1NF: A table is set to be in first NF if we identify the functional dependency.

2NF: A table is set to be in first NF if we identify and delete partial functional dependency.

3NF: A table is set to be in 3rd NF when we identify and delete transitive dependency.

Functional dependency: identify a non key attribute which is depends on key attribute.

Partial functional dependency: identify an attribute which is partially depends on key attribute.

Transitive: identify an key attribute which is independent itself.

Nilesh Gupta

• May 8th, 2007

 

1 NF --> It has only normal form which not support functional dependency.
  It has no multivalue attributes.

2 NF --> Every non key attribute should be depend on key attributes.

3 NF --> No transative dependency.

 x -> y
 y -> z

 here no relation between x & z.

bhawesh

• Jul 19th, 2007

 

First NF---Attribute should be atomic an no redundant row. (functional dependancy)

Second Normal Form : All Non-Key attribute should be fully functionally dependent on primary key.(removes partial dependancy)

Third normal Form : There is no transitivity dependency between attribute.

anbum

• Oct 17th, 2007

 

Normalization is based on the functional dependency and primary key.

1NF- Attribute should be atomic value and there must be no composite attribute, no multivalued attribute and no relation with in relation.
By default what ever relation we are creating in the oracle by default it will be in first normal form

2nf - There is no partial dependency. it is based on the full functional dependency. non key attribute should be fully dependent on the key attribute.

e.g
R={pno,eno,hours,ename,pname,plocation}
given functional dependency
F = {{pno,eno}-> hours,
     eno->ename
     pno->pname, plocation}

in the above relation R ename is dependent on the eno and
pname and plocation are dependent on the pno
so the relation R can be splited in to
R1={pno,eno,hours} 
R2 = {eno,ename} 

R3={pno,pname,plocation}
now all the relations R1, R2 and R3 are in full functional dependency.

3NF -  There is no Transitive dependency.
R={eno,ename,address,dno,dname}
functional dependency
F1={eno->{ename,address,dno}
   dno->dname}
if you have transitive dependency in the relation R then decompose the relation R in to R1 and R2

R1={eno,ename,address,dno}
R2={dno,dname}

def: x->A
x is a super key or A is a prime attribute
in the given dependency F1
dno is not a super key and dname is not a prime attribute.
so, the relation R can be decompose into R1 and R2 and in relation R2 dno make it as a primary key.