Last tested: Aug 31, 2018
Data normalization is the process of improving the logical design of your database so that it satisfies certain constraints that avoid unnecessary duplication of data.
Purpose: The goal of data normalization is to avoid anomalies:
- Insertion Anomaly
- Adding new row forces user to create duplicate data
- Deletion Anomaly
- Deleting one row may cause loss of data that may be needed for other future rows
- Modification Anomaly
- Changing data in one row forces changes in other rows because of duplication
Data Redundancy: When the same piece of data is held in 2 separate places. A positive type of data redundancy works to safeguard data and promote consistency. It is common practice to have a piece of data stored in multiple places, however, the key is to have a centralized field or space for that data, so that there is one place to update all the redundant data.
Referential Integrity: Foreign Key of one table must match the Primary Key of another.
Entity Integrity: All primary key values must contain data values
1st Normal Form
- No multivalued attributes
3rd Normal Form
- 1st Normal rules
- Every non-key attribute is defined by the primary key, not by part of the key
- No partial dependencies