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Old 13th July 2011, 12:40 PM   #1
meena
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Oracle Interview Questions

1.What is First Normal Form
Ans: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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Last edited by meena; 13th July 2011 at 12:42 PM.
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Old 18th July 2011, 11:42 AM   #2
jamshedpur543
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Thanks i hope this helps in my interview but every interview is different for different person
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