Database Systems Evolution Quiz

Study Notes

Database systems were developed in the 1960s and 1970s to solve the problems associated with file-based applications.
File-based applications were unreliable, had data redundancy, and lacked data integrity.

Data models are used to describe data, relationships between data, semantics, and consistency constraints.
Different data models exist, classified into four categories: Relational, Entity-Relationship, Semi-structured, and Object-Based.

The entity-relationship (E-R) model uses entities and relationships between them to represent data.
An entity is a distinguishable object or thing in the real world.
This model is used frequently in database design.

This model allows individual data items of the same type to have different sets of attributes.
This contrasts with other models where every data item of the same type has the same attributes.
JSON and XML are widely used representations for semi-structured data.

Object-oriented programming (OOP) languages like Java, C++, and C# have integrated object-based concepts into database systems.
Database systems allow storing procedures to be executed by the database system.
This extends the relational model with ideas like encapsulation, methods, and object identity.

A university database can be represented with tables, such as an "instructor" table holding details about instructors (ID, Name, Department, Salary) and a "department" table holding details about departments (Dept Name, Building, Budget).
The "instructor" table would show, for example, that an instructor named Einstein with ID 22222 works in the Physics department and earns $95,000 annually.
The "department" table would show, for example, that the Biology department is located in the Watson building and has a budget of $90,000.