Database Systems


This article defines and explains the concept and need of database systems,different types of it, the types of users that operate it,various levels of data abstraction and the types of data models available.

Database Systems



What is a database system? What is its need?
A database is a collection of interrelated data and a database system is basically a computer-based record keeping system.
A typical file processing system suffers from some major limitations like data redundancy (duplication of data), data inconsistency, unsharable data, unstandardized data, insecure data, incorrect data etc. On the other hand, a database system overcomes all these limitations and ensures continuous efficiency. The advantages provided by a database system are:

1. Reduced data redundancy.

2. Controlled data inconsistency.

3. Shared data

4. Standardized data

5. Secured data

6. Integrated data.

Therefore, to have the systems with increased performance and efficiency, the database systems are preferred.

How many types of users work on database systems?
A primary goal of a database system is to provide an environment for retrieving information from and storing new information into the database. These are three different types of database system users, differentiated by the way they expect to interact with the system.

1. End User: An end user is a person who is not a computer-trained person but uses the database to retrieve some information. For example, in a railway reservation system, a customer retrieving the train-details is an end user.

2. Application System Analyst: This user is concerned about the entire database at logical level, i.e., what all data constitutes the database, what are the relationships between the data-entities etc. without considering the physical implementation details.

3. Physical Storage system Analyst: This user is concerned with the physical implementation details of the database such as the storage device to be used, the storage technique to be used, etc.

What are the various levels of data abstraction in a database system?
There are 3 levels of data abstraction:

1. Internal level (Physical level): This level describes how the data is actually stored on the storage medium. At this level, complex low-level data structures are described in details.

2. Conceptual level: This level describes what data are actually stored in the database. It also describes the relationships existing among data. At this level, the database is described logically in terms of simple data structures.

3. External level (View level): This level is concerned with the way the data is viewed by individual users. Only a part of the database relevant to the user(s) is provided to them through this level.

What are the various data models available for database systems?
A data model is a collection of conceptual tools for describing data, data relationships, data semantics etc. There are generally three data models available: relational, network, and hierarchical model.

1. Relational Model: The relational model represents data and relationships among data by a collection of tables known as relations, each of which has a number of columns with unique names.

2. Network model: The network model represents data by collections of records and relationships among data represented by links which can be viewed as pointers. The records in the database are organized as collection of arbitrary graphs.

3. Hierarchical model: The hierarchical model is similar to the network model in the sense that data and relationships among data are represented by records and links respectively. It differs from the network model in that the records are organized as collections of trees rather than arbitrary graphs.


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