What is First Normal Form ?

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Kiran Shetty

  • Jun 24th, 2005
 

An entity is in the first normal form if it contains no repeating groups. In relational terms, a table is in the first normal form if it contains no repeating columns. Repeating columns make your data less flexible, waste disk space, and make it more difficult to search for data. In the telephone directory  
 

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Kenny

  • Jul 18th, 2005
 

First Normal Form (1NF)  
 
A table satisfying the properties of a relation is said to be in first normal form. As discussed in an earlier chapter, a relation cannot have multivalued or composite attributes. This is what the 1NF requires.  
 
A relation is in 1NF if and only if all underlying domains contain atomic values only.  
 
The first normal form deals only with the basic structure of the relation and does not resolve the problems of redundant information or the anomalies discussed earlier. All relations discussed in these notes are in 1NF.  
 
For example consider the following example relation:  
 
 
student (sno, sname, dob)  
Add some other attributes so it has anomalies and is not in 2NF  
 
 
The attribute dob is the date of birth and the primary key of the relation is sno with the functional dependencies sno -> sname and sno -> dob. The relation is in 1NF as long as dob is considered an atomic value and not consisting of three components (day, month, year). The above relation of course suffers from all the anomalies that we have discussed earlier and needs to be normalized. (add example with date of birth)  
 

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vvijaychandra

  • Jun 24th, 2006
 

eliminate the repeating groups in the individual tables

create a seperate table for each set of related data.

identify each set of related data with a primary key

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Sujatars

  • Jun 15th, 2007
 

First Normal Form sets the basic structure for an organized database by
1. Eliminating the duplicate/repetative columns from the same table.
2. Create a seperate table for each set of related data and identify each set of related data (row) with a unique column (primary key).

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