Introduction to Database Design Methodology
Be aware of and appreciate the importance of a good database design in effective database management.
Describe the needs of the three levels of data abstraction, namely conceptual level, physical level and view level.
A database model is used to describe all facts related to an information system.
Example.
Resources management system, the data model of a database is designed to store all the employees' annual leave records. If the manager wants to know how many days of annual leave a certain employee has left to take in that year, the system can help to produce a report to show the annual leave of the employee.
A database design determines how data is stored and how tables (or objects) interrelate with each other.
Effects of database design on a system
Problems of poor database design
1.unnecessary of duplicated data
2.inconsistency modifications
3.Loss of critical data (deletion)
4.introduction of null value (insertion)
5 inconsistency of identifiers.(different name for the same field in different table, data dictionary is important)
So, we have to follow proper procedures in designing a good database.
Good database design
1. Easier to debug
2. better utilization of storage space
3. Higher efficiency
4. higher reliability, enforce data consistency
5. avoid loss of data
6. avoid unnecessary data dependency
7. extended functionalities
Data Abstraction Levels
Conceptual level (Mainly show the relationship, ER diagram, Schema)
View Level (Result of SQL, data extracted from different tables)
Physical Level (How data is stored in storage space)