The concept of functional dependency (also known as normalization was introduced by professor Codd in 1970 when he defined the first three normal forms (first, second and third normal forms). Normalization is used to avoid or eliminate the three types of anomalies (insertion, deletion and update anomalies) which a database may suffer from. These concepts will be clarified soon, but first let us define the first three normal forms.

First Normal Form: A relation is in first normal form if all its attributes are simple. In other words, none of the attributes of the relation is a relation. Notice that relation means 2-diemenatioanl table.

Example -1. Assume the following relation

Student-courses (Sid:pk, Sname, Phone, Courses-taken)

Where attribute Sid is the primary key, Sname is student name, Phone is student's phone number and Courses-taken is a table contains course-id, course-description, credit hours and grade for each course taken by the student. More precise definition of table Course-taken is :

Course-taken (Course-id:pk, Course-description, Credit-hours, Grade)

According to the definition of first normal form relation Student-courses is not in first normal form because one of its attribute Courses-taken is itself a table and is not a simple attribute. To clarify it more assume the above.

Answered by Hemant Singh , an ibibo Master, at 5:15 PM on August 05, 2008

The concept of functional dependency (also known as normalization was introduced by professor Codd in 1970 when he defined the first three normal forms (first, second and third normal forms). Normalization is used to avoid or eliminate the three types of anomalies (insertion, deletion and update anomalies) which a database may suffer from. These concepts will be clarified soon, but first let us define the first three normal forms.

First Normal Form: A relation is in first normal form if all its attributes are simple. In other words, none of the attributes of the relation is a relation. Notice that relation means 2-diemenatioanl table.

Example -1. Assume the following relation

Student-courses (Sid:pk, Sname, Phone, Courses-taken)

Where attribute Sid is the primary key, Sname is student name, Phone is student's phone number and Courses-taken is a table contains course-id, course-description, credit hours and grade for each course taken by the student. More precise definition of table Course-taken is :

Course-taken (Course-id:pk, Course-description, Credit-hours, Grade)

According to the definition of first normal form relation Student-courses is not in first normal form because one of its attribute Courses-taken is itself a table and is not a simple attribute. To clarify it more assume the above

Answered by Sharad Singh , an ibibo Master, at 2:10 PM on August 02, 2008

iam sorry iam not software

Answered by sri vidya , an ibibo Citizen, at 2:27 PM on August 01, 2008

1NF- DATA IS NOT ARRANGED PROPERLY.
2NF-IF TABLE IS IN 1NF AND ALL THE NON KEY ATTRIBUTES
DON'T DEPEND ON EACH OTHER......

Answered by vimal patel at 1:26 PM on August 01, 2008

what is DBMS

Answered by Sushant , an ibibo Citizen, at 10:10 AM on August 01, 2008

What type of help in which prgrame ? Pl. clear to me. -

Answered by Arvind at 8:00 AM on July 31, 2008

In relational database design, the process of organizing data to minimize redundancy. Normalization usually involves dividing a database into two or more tables and defining relationships between the tables. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.
There are three main normal forms, each with increasing levels of normalization:

First Normal Form (1NF): Each field in a table contains different information. For example, in an employee list, each table would contain only one birthdate field.
Second Normal Form (2NF): Each field in a table that is not a determiner of the contents of another field must itself be a function of the other fields in the table.
Third Normal Form (3NF): No duplicate information is permitted. So, for example, if two tables both require a birthdate field, the birthdate information would be separated into a separate table, and the two other tables would then access the birthdate information via an index field in the birthdate table. Any change to a birthdate would automatically be reflect in all tables that link to the birthdate table.

There are additional normalization levels, such as Boyce Codd Normal Form (BCNF), fourth normal form (4NF) and fifth normal form (5NF). While normalization makes databases more efficient to maintain, they can also make them more complex because data is separated into so many different tables.

The concept of functional dependency (also known as normalization was introduced by professor Codd in 1970 when he defined the first three normal forms (first, second and third normal forms).

Answered by Ashish Yadav , an ibibo Wizard, at 2:36 PM on July 30, 2008

well malvika,In relational database design, the process of organizing data to minimize redundancy. Normalization usually involves dividing a database into two or more tables and defining relationships between the tables. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.
There are three main normal forms, each with increasing levels of normalization:

First Normal Form (1NF): Each field in a table contains different information. For example, in an employee list, each table would contain only one birthdate field.
Second Normal Form (2NF): Each field in a table that is not a determiner of the contents of another field must itself be a function of the other fields in the table.
Third Normal Form (3NF): No duplicate information is permitted. So, for example, if two tables both require a birthdate field, the birthdate information would be separated into a separate table, and the two other tables would then access the birthdate information via an index field in the birthdate table. Any change to a birthdate would automatically be reflect in all tables that link to the birthdate table.

There are additional normalization levels, such as Boyce Codd Normal Form (BCNF), fourth normal form (4NF) and fifth normal form (5NF). While normalization makes databases more efficient to maintain, they can also make them more complex because data is separated into so many different tables.

The concept of functional dependency (also known as normalization was introduced by professor Codd in 1970 when he defined the first three normal forms (first, second and third normal forms).

Answered by Debashis , an ibibo Master, at 10:34 AM on July 30, 2008

well, Functional Dependencies and Normalization
• FDs are the basis of normalization -- a formal
methodology for refining and creating good
relational designs
• Normalization places some constraints on the
schema to:
– Reduce redundancy
– Alleviate update anomalies
– Reduce the pressure to have null values
• Normalization puts relations in good form!
• Normalization is a solved problem (all algorithms
& proofs are worked out)
Schema Refinement Techniques
• Decomposition starts with an ER diagram, and
uses the FDs to guide the schema design and
decomposition, e.g., to replace a relation
R(ABCD) with, two relations, say R1(AB) and
R2(BCD) using the project operator.
• Synthesis is another refinement technique
which takes all attributes over the original
relation R, a set of FDs over these attributes,
and constructs a good schema
EMP(ENAME, SSN, BDATE, ADDRESS, DNUM, DNAME, DMGRSSN)
EMP_PROJ(SSN, PNUM, HOURS, ENAME, PNAME, PLOCATION)
What are the FDs?
EMP(ENAME, SSN, BDATE, ADDRESS, DNUM, DNAME, DMGRSSN)


Source : http://www.cs.utah.edu/classes /cs5530/Lectures/lecture9-fds. pdf

Answered by Yash , an ibibo Master, at 8:31 PM on July 29, 2008

Hi Malvika,

Normalization is the process of efficiently organizing data in a database. There are two goals of the normalization process: eliminating redundant data (for example, storing the same data in more than one table) and ensuring data dependencies make sense (only storing related data in a table). Both of these are worthy goals as they reduce the amount of space a database consumes and ensure that data is logically stored.

Say for example: If you are designing a database to store Marks information, you should have student details in one table and corresponding marks details of each student (linked with an ID) to a separate table.

There are generally 4 types of Normalization, 1 NF, 2NF, 3NF and 4 NF.
First Normal Form (1NF)
First normal form (1NF) sets the very basic rules for an organized database:

* Eliminate duplicative columns from the same table.
* Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).

Second Normal Form (2NF)
Second normal form (2NF) further addresses the concept of removing duplicative data:

* Meet all the requirements of the first normal form.
* Remove subsets of data that apply to multiple rows of a table and place them in separate tables.
* Create relationships between these new tables and their predecessors through the use of foreign keys.

Third Normal Form (3NF)
Third normal form (3NF) goes one large step further:

* Meet all the requirements of the second normal form.
* Remove columns that are not dependent upon the primary key.

Fourth Normal Form (4NF)
Finally, fourth normal form (4NF) has one additional requirement:

* Meet all the requirements of the third normal form.
* A relation is in 4NF if it has no multi-valued dependencies.

In our software development, we generally go till 3NF, because 4NF is resource consuming and generally slows down the performance.

If you need more info on DB, you can always contact me.

You can also visit the following links for more information:
http://www.rsolu tions.net/RSweb/Normalization/
http://www.devshed.com/c/a/M ySQL/An-Introduction-to-Databa se-Normalization/

All the best!!
Sachin

Answered by Sachin Das , an ibibo Specialist, at 5:41 PM on July 29, 2008