Question

Consider the ERD where the entity type Employee has one key attribute, id, and the entity type Position has one key attribute, title. As well the ERD shows a one-to- many relationship assigned to which can be expressed as: An employee is assigned to at most one position. A position can be assigned to many employees.

Short answer

The structure of the database will consist of two tables, Employee and Position. Each Employee is linked to a Position through a foreign key – 'PositionTitle', referring to the 'title' attribute in the Position table. This represents a 'one-to-many' relationship where one position can be associated with multiple employees.

Step-by-step solution

Understanding the ERD Entities

The problem consists of two entities: 'Employee' and 'Position'. Each 'Employee' has a unique 'id' serving as a key attribute. Similarly, each 'Position' has a unique 'title' as a key attribute.

Understanding the Relationship

In a 'one-to-many' relationship, each 'Employee' can be assigned to at most one 'Position'. In contrast, a single 'Position' can be assigned to many 'Employees'. This is represented as 1:N relationship, where N represents many.

Implementation

In terms of database structure, two tables can be created - one for 'Employee' and the other for 'Position'. Both tables will be linked through the foreign key. The Employee's table will include the field 'PositionTitle' as a foreign key which maps to the key attribute 'title' from Position table.

Key concepts

Understanding Entity-Relationship Diagrams

In the field of database design, an entity-relationship diagram (ERD) plays a crucial role. It visually represents the data that will be stored in a database and the relationships between different types of data. An ERD includes entities, which are essentially objects or concepts that can have data stored about them, like 'Employee' and 'Position'.

Entities have attributes, which are pieces of information tied to them; for example, the 'id' of an Employee or the 'title' of a Position are attributes. A key attribute, specifically, uniquely identifies each instance of an entity; thus 'id' and 'title' are key attributes in our case.

Relationships describe how entities interact with each other, such as the 'one-to-many' relationship seen in this exercise, where one position can be assigned to multiple employees. To accurately convey this in an ERD, lines or arrows are used to connect entities, with symbols indicating the nature of the relationship, like the '1:N' notation for one-to-many.

Database Key Attributes Explained

A key attribute is an element that acts as a unique identifier within a database entity. In the context of this exercise, every 'Employee' has an 'id', and every 'Position' has a 'title', both serving as primary keys. These key attributes are crucial in maintaining data integrity and enabling the efficient querying and management of a database.

The importance of key attributes extends to their role in relationships. In a one-to-many relationship, the primary key of the 'one' side (in this case, 'Position') can become a foreign key in the 'many' side ('Employee'). This foreign key establishes a referential link between the two entities. For example, 'PositionTitle' in the 'Employee' table refers back to the 'Position' entity, maintaining data consistency and supporting relational operations.

Relational Database Design Fundamentals

Relational database design involves structuring a database in accordance with the principles of entities and their relationships to ensure data is stored efficiently and can be reliably retrieved. In our exercise, the design process would begin with defining the entities ('Employee' and 'Position') and their attributes ('id' and 'title', respectively).

Following the identification of entities and attributes, establishing the proper relationships is next. As 'Employee' is related to 'Position' with a one-to-many relationship, this will dictate the structure of the database tables and the use of foreign keys. A well-designed relational database promotes the elimination of unnecessary data duplication and supports data integrity. Utilizing an ERD during the design phase can greatly aid in visualizing the final structure and relationships of the database.