Schema refinement in DBMS

Schema refinement

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

Update anomalies.

Deletion anomalies.

Insertion anomalies.

            Update anomalies

An update anomaly is a data inconsistency that results from data redundancy and a partial update.

Deletion anomalies

            A deletion anomaly is the unintended loss of data due to deletion of other data.

           

            Insertion anomalies

An insertion anomaly is the inability to add data to the database due to absence of other data.

           

            Also there is need to do more work in normalization other than avoiding anomalies

·         Identify functional dependencies.

·         Applying rules for normalization.

·         Normalizing multi value attributes.