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Data & Analytics · Intermediate

Data Anomalies

Insert, update and delete anomalies: integrity problems caused by redundant data in unnormalized tables.

Definition

An insertion anomaly prevents recording a fact without an unrelated fact, an update anomaly leaves copies of a value inconsistent, and a deletion anomaly loses information when a row is removed. Normalization eliminates these by storing each fact once.

Example

Deleting the last employee of a department also deletes the only record of that department's name (deletion anomaly).

Exam tip

The purpose of normalization in exam wording is 'to eliminate redundancy and insert/update/delete anomalies'.

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