Data modeling is the process of creating a visual representation (model) of how data is structured and related within a database system, aiding in understanding and designing the database efficiently.
Represents a distinct object, concept, or thing in the real world that data will be stored about (e.g., “Customer” or “Product”).
Characteristics or properties that describe the entities and are stored as fields in the database (e.g., “Name” or “Price”).
Defines how entities are related to each other and helps establish connections between different entities (e.g., “One-to-Many” or “Many-to-Many”).
Each record in one entity is related to only one record in another entity.
Each record in one entity can be related to multiple records in another entity.
Records in both entities can be related to multiple records in each other.
Referential keys are an essential concept in database design that establishes relationships between tables, ensuring data integrity and maintaining consistency between related records.
A primary key is a unique identifier for each record in a table, ensuring that each row has a distinct value, and it serves as a reference point for other tables’ foreign keys.
A foreign key is a field in one table that establishes a link to the primary key of another table, creating relationships between different tables in the database.records.
Let’s consider an example of two tables: “Students” and “Class” to understand relationships and referential keys:
| StudentID | StudentName | ClassID |
|---|---|---|
| 101 | John Smith | 1 |
| 102 | Jane Doe | 2 |
| 103 | Michael Brown | 1 |
| ClassID | ClassName |
|---|---|
| 1 | Math Class |
| 2 | Science Class |
| 3 | English Class |
In this example, there is a “One-to-Many” relationship between the “Class” table and the “Students” table. One class can have multiple students (e.g., Math Class can have John Smith and Michael Brown).
– In the “Students” table, the “StudentID” is the primary key, serving as a unique identifier for each student.
– In the “Class” table, the “ClassID” is the primary key, uniquely identifying each class.
The “ClassID” field in the “Students” table serves as a foreign key, linking the students to their respective classes. For example, the value “1” in the “ClassID” field for John Smith and Michael Brown refers to the “Math Class” in the “Class” table.
Using referential keys and establishing relationships, we can ensure data integrity, avoid data duplication, and efficiently retrieve data related to students and their classes.
The Entity Relationship (ER) Model is a conceptual data model used in database design to visualize and represent the relationships between entities (objects or concepts) in a database system.
An ER diagram is a graphical representation of the ER Model, illustrating the entities, their attributes, and the relationships between entities in a clear and concise manner.
Represented by a rectangle with the entity name inside, it signifies an object or concept in the real world (e.g., “Customer” or “Product”).
Depicted by an oval shape connected to the entity, it represents a characteristic or property of the entity (e.g., “Name” or “Age”).
Shown by a diamond shape connecting entities, it illustrates the association between two or more entities (e.g., “One-to-Many” or “Many-to-Many”).