What is the Difference Between Entity Type and Entity Set

The main difference between Entity Type and Entity Set is that Entity Type refers to the category an entity belongs to while Entity Set refers to all the entities of an entity type.

Relational Database Management System (RDBMS) is a database management system that is based on the relational model. Moreover, these systems store data in tables and the tables are related to each other. In a table, each record is called an entity. The category of a particular entity in the table is called the entity type while the collection of all the entities in the table is called an entity set.

Key Areas Covered

1. What is Entity Type
     – Definition, Functionality
2. What is Entity Set
    – Definition, Functionality
3. What is the Difference Between Entity Type and Entity Set
     – Comparison of Key Differences

Key Terms

Entity, Entity Type, Entity Set, RDBMS

What is Entity Type

In an RDBMS table, each record is called an entity. Entity type is the category to which the entity belongs. For instance, assume a university management system. It has a table called Student.

In the above table, record id=1, name= Anne, age=21 is a record. It is an entity. Likewise, each record in the Student table is an entity. They all belong to Student. In other words, each record represents a Student object. Therefore, Student is the entity type. Similarly, a record in the Lecturer table is an entity and it is of type Lecturer.

What is Entity Set

The complete data set of all entities is called the entity set. In the above table, the entity set consists of all the records. In other words, the records with id 1, 2 and 3 represent the entire data set. It is the entity set. Therefore, entity set refers to all records in the Student table. Overall, the entity set denotes all records of a specific entity type.

Difference Between Entity Type and Entity Set

Definition

Entity type is the category of a particular entity in the table of an RDBMS; in contrast, entity set refers to the collection of all entities of the same entity type in RDBMS. Thus, this is the main difference between Entity Type and Entity Set.

Relationship with Tables

Another difference between Entity Type and Entity Set is that the name of the table is the entity type while all rows of the table are the entity set.

Example

In a student table, each entity is of type student. However, all the records in the student table represent the entity set.

Conclusion

RDBMS is one of the most popular database management systems. Many enterprise level applications use it to store and manage data. Furthermore, RDBMS stores data in tables; we call these tables relations. Entity type and entity set are two common terms in RDBMS. The main difference between Entity Type and Entity Set is that Entity Type refers to the category an entity belongs to while Entity Set refers to all the entities of an entity type.

Reference:

1. Entity, Entity Type, Entity Set | Database Management System, Techtud, 14 July 2014, Available here.