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What is Normalization, First Normal Form, Second Normal Form , Third Normal Form


Answer posted by Badri Santhosh on 2005-05-18 09:40:29: Normalization : The process of decomposing tables to eliminate data redundancy is called Normalization. 
 
1N.F:- The table should caontain scalar or atomic values. 
2 N.F:- Table should be in 1N.F + No partial functional dependencies 
3 N.F :-Table should be in 2 N.F + No transitive dependencies
Asked by: Interview Candidate | Asked on: Jul 28th, 2005
Showing Answers 1 - 6 of 6 Answers
Badri Santhosh

Answered On : May 18th, 2005

Normalization : The process of decomposing tables to eliminate data redundancy is called Normalization. 
 
1N.F:- The table should caontain scalar or atomic values. 
2 N.F:- Table should be in 1N.F + No partial functional dependencies 
3 N.F :-Table should be in 2 N.F + No transitive dependencies

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ramesh

Answered On : Jun 7th, 2005

2NF - table should be in 1NF + non-key should not dependent on subset of the key ({part, supplier}, sup address) 
 
3NF - table should be in 2NF + non key should not dependent on another non-key ({part}, warehouse name, warehouse addr) 
 
{primary key} 
 
more... 
4,5 NF - for multi-valued dependencies (essentially to describe many-to-many relations)

  
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murali

Answered On : Jul 28th, 2005

Normalization can be defined as segregating of table into two different tables, so as to avoid duplication of values. 
The normalization is a step by step process of removing redundancies and dependencies of attributes in data structure 
 
The condition of data at completion of each step is described as a normal form. 
Needs for normalization : improves data base design. 
Ensures minimum redundancy of data. 
Reduces need to reorganize data when design is modified or enhanced. 
Removes anomalies for database activities. 
 
First normal form : 
A table is in first normal form when it contains no repeating groups. 
The repeating column or fields in an un normalized table are removed from the table and put in to tables of their own. 
Such a table becomes dependent on the parent table from which it is derived. 
The key to this table is called concatenated key, with the key of the parent table forming a part it. 
 
Second normal form: 
A table is in second normal form if all its non_key fields fully dependent on the whole key. 
This means that each field in a table ,must depend on the entire key. 
Those that do not depend upon the combination key, are moved to another table on whose key they depend on. 
Structures which do not contain combination keys are automatically in second normal form. 
Third normal form: 
A table is said to be in third normal form , if all the non key fields of the table are independent of all other non key fields of the same table. 

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ravi kumar guturi

Answered On : Mar 9th, 2006

Normalization is a process of remove the retundancy and inconsistency

Mainly 3 normal forms

1normal form: Here contain only atomic values

2normal form:The nonkey values must be depend upon the primary key

3normal form:not depended on transitivity

  
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Jyothsna Tallapally

Answered On : May 10th, 2006

Normalization:It is the process of efficiently organizing data in a database.There are 2-goals of the normalization process: 1. Eliminate redundant data 2. Ensure data dependencies make sense(only storing related data in a table)First Normal Form:It sets the very basic rules for an organized database. 1. Eliminate duplicate columns from the same table 2. Create separate tables for each group of related data and identify each row with a unique column or set of columns.Second Normal Form:Further addresses the concept of removing duplicative data. 1.Remove subsets of data that apply to multiple rows of a table and place them in a separate tables. 2.Create relationships between these new tables and their predecessors through the use of foreign keys.Third Normal Form: 1.Remove columns that are not dependent upon the primary key.Fourth Normal Form: 1.A relation is in 4NF if it has no multi valued dependencies.These normalization guidelines are cumulative.For a database to be in 2NF, it must first fulfill all the criteria of a 1NF database.

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dstorkey

Answered On : Mar 24th, 2009

View all answers by dstorkey

To paraphrase the oath, and help you remember, in 3rd normal form data in the table depends on the key, the whole key, and nothing but the key.

  
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