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Difference between Data Redundancy and Data Inconsistency

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  • Difficulty Level : Hard
  • Last Updated : 26 Apr, 2022
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Overview :
Data Redundancy and Data Inconsistency are the important terms used in the Database. A good Database Design is the one in which there is minimum Data Redundancy and Data Inconsistency. In this article, we will tell what are these two terms and what is the difference between them.

Data Redundancy
It is defined as the redundancy means duplicate data and it is also stated that the same parts of data exist in multiple locations into the database. This condition is known as Data Redundancy. 

Problems with Data Redundancy :
Here, we will discuss the few problems with data redundancy as follows.

  1. Wasted Storage Space.
  2. More Difficult Database Update.
  3. It will lead to Data Inconsistency. 
  4. Retrieval of data is slow and inefficient.

Example –
Let us take an example of a cricket player table.

Step-1 :
Consider cricket player table as follows. 

Player NamePlayer AgeTeam NameTeam ID
Virat Kohli32India1
Rohit Sharma34India1
Ross Taylor37New Zealand2
Shikhar Dhawan35India1
Kane Williamson30New Zealand2

Step-2 :
We can clearly see that the Team Name and Team Id are repeated at multiple places. we can make a separate table to store this information and reduce data redundancy.

Player NamePlayer AgeTeam Id
Virat Kohli321
Rohit Sharma341
Ross Taylor372
Shikhar Dhawan351
Kane Williamson302

Step-3 :
This is known as Normalization used to reduce Data Redundancy.

Team IdTeam Name
2New Zealand

Data Inconsistency : 
When the same data exists in different formats in multiple tables. This condition is known as Data Inconsistency. It means that different files contain different information about a particular object or person. This can cause unreliable and meaningless information. Data Redundancy leads to Data Inconsistency. 

Example – 
If we have an address of someone in many tables and when we change it in only one table and in another table it may not be updated so there is the problem of data inconsistency may occur.

Differences :

TopicData RedundancyData Inconsistency
ConditionIt will be applicable when the duplicate data exists in multiple places in the database.It will be applicable when the duplicate data exists in different formats in multiple tables.
How to minimize it? we can use normalization to minimize Data Redundancy.we can use constraints on the database to minimize Data Inconsistency.
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