Wikia

Database Management

Data Anomalies

Talk0
108pages on
this wiki

Category page

       ulul         Normalization is the process of splitting relations into well structured relations that allow users to inset, delete, and update tuples without introducing database inconsistencies. Without normalization many problems can occur when trying to load an integrated conceptual model into the DBMS. These problems arise from relations that are generated directly from user views are called anomalies. There are three types of anomalies: update, deletion and insertion anomalies.

An update anomaly is a data inconsistency that results from data redundancy and a partial update. For example, each employee in a company has a department associated with them as well as the student group they participate in.

Employee_ID

Name

Department

Student_Group

143 Sambu ssds dsds

123

J. Longfellow

Accounting

dBeta Alpha Psi

234

B. Rech

Marketing

Marketing Club

345

B. Rech

Marketing

Management Club

456

A. Bruchs

CIS

Technology Org.

567

A. Bruchs

CIS

Beta Alpha Psi


If A. Bruchs’ department is an error it must be updated at least 2 times or there will be inconsistent data in the database. If the user performing the update does not realize the data is stored redundantly the update will not be done properly.

A deletion anomaly is the unintended loss of data due to deletion of other data. For example, if the student group Beta Alpha Psi disbanded and was deleted from the table above, J. Longfellow and the Accounting department would cease to exist. This results in database inconsistencies and is an example of how combining information that does not really belong together into one table can cause problems.

An insertion anomaly is the inability to add data to the database due to absence of other data. For example, assume Student_Group is defined so that null values are not allowed. If a new employee is hired but not immediately assigned to a Student_Group then this employee could not be entered into the database. This results in database inconsistencies due to omission.

Update, deletion, and insertion anomalies are very undesirable in any database. Anomalies are avoided by the process of normalization.

Pages in category "Data Anomalies"

This category contains only the following page.

Around Wikia's network

Random Wiki