meaning of data redundency
gauravtomar14:
Redundancies can be detected by correlation analysis.For attributes that are numeric correlation coffiecient or covariance may be suitable.Whereas in nominal data we employ chi square test.
Redundancy is an important issue while dealing with data integration.
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Data redundancy is a condition created within a database or datastorage technology in which the same piece of data is held in two separate places. This can mean two different fields within a single database, or two different spots in multiple software environments or platforms.
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Data redundancy means that thesame data are not present in one and only place.
It could be related to hardware but itmay also meanthat, in a Database, the same data are in multiple tables, mainly for performance reason. For example, in an Order table, you usually getan User ID as foreign key related to the user who has ordered a product. If you want to avoid having to makea join on the User table each time you want to get thename of the user, you couldinclude the name of the user in the Order table. The name of the user is in both Order andUser tables. That is data redundancy and it improves the performance ofthe system. But you don't have to forget to update the name of the user in both tables.
When there is such data redundancy, it affects your data model and more precisely the normal forms.
It could be related to hardware but itmay also meanthat, in a Database, the same data are in multiple tables, mainly for performance reason. For example, in an Order table, you usually getan User ID as foreign key related to the user who has ordered a product. If you want to avoid having to makea join on the User table each time you want to get thename of the user, you couldinclude the name of the user in the Order table. The name of the user is in both Order andUser tables. That is data redundancy and it improves the performance ofthe system. But you don't have to forget to update the name of the user in both tables.
When there is such data redundancy, it affects your data model and more precisely the normal forms.
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