|
INTERVIEW QUESTIONS
CONCEPTS AND ARCHITECTURE
DATA MODELING
DETAILS
Question: What is First Normal Form
Answer: 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)
|
|
|
Category |
Data Modeling Interview Questions & Answers -
Exam Mode /
Learning Mode
|
Rating |
(0.2) By 7796 users |
Added on |
7/24/2011 |
Views |
71583 |
Rate it! |
|
|
Question:
What is First Normal Form
Answer:
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) Source: CoolInterview.com
If you have the better answer, then send it to us. We will display your answer after the approval.
Rules to Post Answers in CoolInterview.com:-
- There should not be any Spelling Mistakes.
- There should not be any Gramatical Errors.
- Answers must not contain any bad words.
- Answers should not be the repeat of same answer, already approved.
- Answer should be complete in itself.
|
|
Related Questions |
View Answer |
|
Waht is second normal form
|
View Answer
|
|
What is an artificial (derived) primary key? When should it be used?
|
View Answer
|
|
Why are recursive relationships are bad? How do you resolve them?
|
View Answer
|
|
Describe the third normal form
|
View Answer
|
|
Is this statement TRUE or FALSE – all databases must be in third normal form?
|
View Answer
|
|
What is ERD?
|
View Answer
|
|
When should you consider denormalization?
|
View Answer
|
|
What is the difference between hashed file stage and sequential file stage in relates to DataStage Server
|
View Answer
|
|
What is data sparsity and how it effect on aggregation?
|
View Answer
|
|
What is the difference between star flake and snow flake schema?
|
View Answer
|
Please Note: We keep on updating better answers to this site. In case you are looking for Jobs, Pls Click Here Vyoms.com - Best Freshers & Experienced Jobs Website.
View All Data Modeling Interview Questions & Answers - Exam Mode /
Learning Mode
|