we can say that a database is in normalized form if
There is no redundant data (for example, storing the same data in more than one table)
*and data dependencies make sense (only storing related data in a table).

Answered by Ashish , an ibibo Wizard, at 2:06 AM on December 26, 2007

The normal forms defined in relational database theory represent guidelines for record design. The normalization rules are designed to prevent update anomalies and data inconsistencies. First normal form [1] deals with the "shape" of a record type. Under first normal form, all occurrences of a record type must contain the same number of fields. First normal form excludes variable repeating fields and groups. This is not so much a design guideline as a matter of definition. Relational database theory doesn't deal with records having a variable number of fields. Second and third normal forms [2, 3, 7] deal with the relationship between non-key and key fields while Fourth [5] and fifth [6] normal forms deal with multi-valued facts.

Answered by @ , an ibibo Master, at 10:57 PM on December 25, 2007

Database normalization is a technique for designing relational database tables to minimize duplication of information and, in so doing, to safeguard the database against certain types of logical or structural problems, namely data anomalies,..A table that is not sufficiently normalized can suffer from logical inconsistencies of various types, and from anomalies involving data operations. In such a table:an update anomaly,an insertion anomaly,a deletion anomaly.

A table is in first normal form (1NF) if and only if it faithfully represents a relation. Given that database tables embody a relation-like form, the defining characteristic of one in first normal form is that it does not allow nulls or duplicate rows.

Answered by rohitud , an ibibo Citizen, at 9:47 PM on December 25, 2007

he normal forms (abbrev. NF) of relational database theory provide criteria for determining a table's degree of vulnerability to logical inconsistencies and anomalies. The higher the normal form applicable to a table, the less vulnerable it is to such inconsistencies and anomalies. Each table has a "highest normal form" (HNF): by definition, a table always meets the requirements of its HNF and of all normal forms lower than its HNF; also by definition, a table fails to meet the requirements of any normal form higher than its HNF.

Answered by pooja , an ibibo Master, at 6:33 PM on December 25, 2007

Normalization is based on the functional dependency and primary key.

Answered by quadeer , an ibibo Specialist, at 5:54 PM on December 25, 2007

Database normalization is a technique for designing relational database tables to minimize duplication of information and, in so doing, to safeguard the database against certain types of logical or structural problems, namely data anomalies. For example, when multiple instances of a given piece of information occur in a table, the possibility exists that these instances will not be kept consistent when the data within the table is updated, leading to a loss of data integrity. A table that is sufficiently normalized is less vulnerable to problems of this kind, because its structure reflects the basic assumptions for when multiple instances of the same information should be represented by a single instance only.

Higher degrees of normalization typically involve more tables and create the need for a larger number of joins, which can reduce performance. Accordingly, more highly normalized tables are typically used in database applications involving many isolated transactions (e.g. an Automated teller machine), while less normalized tables tend to be used in database applications that do not need to map complex relationships between data entities and data attributes (e.g. a reporting application, or a full-text search application).

Database theory describes a table's degree of normalization in terms of normal forms of successively higher degrees of strictness. A table in third normal form (3NF), for example, is consequently in second normal form (2NF) as well; but the reverse is not always the case.

Although the normal forms are often defined informally in terms of the characteristics of tables, rigorous definitions of the normal forms are concerned with the characteristics of mathematical constructs known as relations. Whenever information is represented relationally, it is meaningful to consider the extent to which the representation is normalized.

Answered by expert , an ibibo Specialist, at 4:41 PM on December 25, 2007

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).The normal forms of relational database theory provide criteria for determining a table's degree of vulnerability to logical inconsistencies and anomalies.

Answered by Kajal , an ibibo Master, at 4:35 PM on December 25, 2007

Normal Form in Database is called as Normalization.
Normalization is the process of efficiently organizing data in a database.

There are two goals of the normalization process:
1) Eliminating redundant data (for example, storing the same data in more than one table)
2) 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.

The Normal Forms ::::
The database community has developed a series of guidelines for ensuring that databases are normalized. These are referred to as normal forms and are numbered from one (the lowest form of normalization, referred to as first normal form or 1NF) through five (fifth normal form or 5NF). In practical applications, you will often see 1NF, 2NF, and 3NF along with the occasional 4NF.


First normal form (1NF) sets the very basic rules for an organized database:

a) Eliminate duplicative columns from the same table.
b) 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) further addresses the concept of removing duplicative data:

a) Meet all the requirements of the first normal form.
b)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) goes one large step further:

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

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

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

Answered by alokgupta14 , an ibibo Guru, at 3:50 PM on December 25, 2007