Introduction
Welcome to my Databases blog. This is where I document my learning progress for all things related to this module. It's a little empty right now, but there's definitely more to come. :)
Objectives
- To understand and analyse data required by an organisation and to represent this information requirement using a modelling technique.
- Transform data model to database tables.
- To create and manipulate tables using a well-accepted language, SQL.
What is a Database
File-Based System
- Collection of application programs, each managing its own data.
- Each application program defines and handles its own data files independently of others.
- Sharing of data between applications is likely to be limited.
Issues with File-Based System
- Duplication:
- Different applications may have to use the same information. However, since each application has its own file and sharing of data between applications is limited, data will be duplicated.
- Separation and Isolation:
- Data is scattered among different files, with each file belonging to a single application used by a single department. A department will only have access to its own files but no access to the files of other departments. Files belonging to different departments cannot be used together in order to create more complex data or analysis.
- Program-data dependence:
- Each file belongs to a certain application program. The physical structure of data is defined inside the application program. This could easily, lead to incompatible file formats between applications, meaning that it becomes impossible to share data between them.
Database System
A database system is an organised collection of logically-related data (including its description) that is shared across related applications as part of the information system of an organisation.
- Different departments are able to share the data in the database.
Database Application Life Cycle
Database Planning → System Definition → Analysis → Database Design → Implementation → Testing → Operational Maintainance
| Step | Description |
|---|---|
| Database Planning | Define mission statement of database |
| System Definition | Identify system boundaries |
| Analysis | Collecting and analysing information |
| Implementation | Creating table |
| Testing | Using query languages to test links |
| Operational Maintainance | Go live, continous maintainance |
Database Design
Conceptual Database Design → Logical Database Design → Physical Database Design
| Step | Description |
|---|---|
| Conceptual Database Design | Modelling |
| Logical Database Design | Mapping entity to relation |
| Physical Database Design | Transforming relation to table |