3NF – What is the 3NF example?

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A relation is in 3NF(What is the 3NF example) or the third normal form if and only if it is in 2NF and every non-key attribute is non-transitively dependent on the primary key. By the transitive functional dependency, we mean that If x(primary key) -> y and y->z then x->z.

So, z is transitively dependent on x. According to the definition of 3NF, as such dependency should be there, that is a relation|What is the 3NF example|

within this blog post(What is the 3nf example), we are going to cover What is the 3nf example? What are 1nf 2nf 3nf? What is a relation in 3nf? How do I get a 3nf? 1NF, 2NF, 3NF, BCNF vs 3NF, 1NF, 2NF, 3NF with example PDF, Transitive dependency 3NF, 1st, 2nd, and 3rd normal form examples, Normalization, Step by step normalization example.

Steps for transforming the relation from 2NF to 3NF|What is the 3NF example?

Determine the non-key attributes that determine some other non-key attributes.
Male separate relations take the first one as a primary key.

In simple language, we can say that we try to find attributes that show transitive dependency between them. this we can search from the FD diagram.

Try to avoid this transitivity by using the steps given above.

FD-diagram-in-3NF — **FD-Diagram in 3NF**

In our example given in the above fig., we can say that about S

S#->City
City->Status
S#-> Status

So, this shows transitive dependency, which we have to remove. Other relationships between P and SP do not show any such dependency.

So, in following step 1, we determine the non-key attribute that determines some other non-key attribute.

A city that is a non-key attribute determines the status which is a non-key attribute. That is for any two equal values of the city, status has equal values.

The relation can be shown below.

Relation SC

S#	City
S1	Paris
S2	London
S3	Italy
S4	India
S5	Paris

Relation CS

City	Status
Paris	10
London	20
Italy	30
India	40

Relation SP

S#	P#	Qty
S1	P1	300
S1	P2	100
S2	P3	500
S3	P4	200
S3	P1	450
S4	P5	400
S5	P2	250

Relation P

P#	Pname	`Color
P1	Bulb	Pink
P2	Tubes	Yellow
P3	Fan	Green
P4	Cooler	Black
P5	Lamp	White

The advantage of 3NF is that we can solve the problem that we were facing in 2NF. The solution is explained given below.

Insert:

About CS, we can insert a tuple indicating that a particular city has a particular status. So, we can say that the supplier in Italy must have status 30.

Delete:

On deleting any tuple from relation SC, we don’t lose information about the status of the city in which that supplier lives.

For example: if we delete the second relation from a tuple SC, then we also know that the city of London has status 20.

Update:

If we want to change the status of any city then we just update one tuple about CS.

For Example: IF we wish to change the status of London from 20 to 50 then we have to just update the second tuple about CS. Even now the problem is not fully solved. For this, we go for further normalization.

Check out some related blog posts on Normalization:

What is Normalization and why is it needed?

What is 1NF in DBMS?

What is 2NF in DBMS?

What is BCNF in DBMS?

You can also go through a few more amazing blog links related to DBMS below:

Composite key: Composite key vs Super key…
What is the null value Problem in DBMS…
What is the super key in DBMS…
What is a candidate key in DBMS…
What is Key in DBMS…
BCNF – Boyce Codd Normal Form…
3NF – Third normal form…
2NF – Second Normal Form…
What is1NF(First Normal Form)…
What is normalization with an example…
What do you mean by distributed DBMS and what are its types…
What is DBMS ARCHITECTURE…
DBMS vs RDBMS: What is the main difference between DBMS and RDBMS…
What are the functions of DBA in DBMS…
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Conclusion:

The 3NF(What is the 3NF example) or third normal form is all about the introduction of the foreign key in our relation to reduce the redundancy. To solve the problem coming in 2NF we further break the data table to make some new relations. Here we solve the problem of insertion, deletion, and updating to a certain extent. However, it is never possible to solve all the problems as it is quite difficult to finish the redundancy.

We have gone through the What is 3nf example. What are 1nf 2nf 3nf? What is a relation in 3nf? How do I get a 3nf? 1NF, 2NF, 3NF, BCNF vs 3NF, 1NF, 2NF, 3NF with example PDF, Transitive dependency 3NF, 1st, 2nd, and 3rd normal form examples, Normalization, Step by step normalization example|What is the 3nf example|

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