04 August, 2016

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Database: Difference between repetition and redundancy



Student name
Address
Tony
Seattle
James
Seattle
Alex
Seattle
Thomas
Seattle
Amar
Seattle

This table represents Student’s name and their address. We can see here that all the students have same address. Is the data redundant here? Are we wasting memory? No. The data here will not be called redundant. Its just repetition of data that we see here.

Lets take another example:

Student ID
Student name
email
course
duration
fee
100
Tony
Oracle
60
10000
200
James
Oracle
60
10000
300
Alex
Oracle
60
10000
400
Thomas
Oracle
60
10000
500
Amar
Oracle
60
10000

Is the data redundant here? Is it wastage of memory? Yes.
The repetition of data caused by the existing functional dependency which is causing wastage of memory is called redundancy.

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