To understand Database management system(DBMS) basically, you should know what an entity is in DBMS. Database management systems are vital for effective data management, storing and retrieval. A key concept in DBMS is the entity. An entity in DBMS represents real-world objects such as people, products, or events that are stored as data.
DBMS is essential in domains like data science, machine learning, and business intelligence because it ensures data consistency, minimizes redundancy, and gives multi-user access.
This blog will help you understand the aspect of entity in DBMS, explore its types, entity sets in DBMS, understand their real-world applications, and provide a career guide.
An entity is a thing or object in the real world that contains attributes that describe it. In DBMS, an entity refers to a piece of data stored within the database. It can be said to be a tree-like structure. An entity can represent any person, place, thing, or event that requires storage within the database.
This is important in database design because entities are the fundamental components of information kept and controlled in a database. For example, a car, a student, and a bank account are all considered entities, as each has a roll number, registration number, account number, address, bank branch, etc. that can identify it.
For example, a car has different attributes like color, model, year, etc., and a bank has characteristics like branch name, IFSC code, bank name, ID, cheque number, etc.
An entity set is a collection of the same type that shares the exact attributes. For instance, all students of a school are an entity set of student entities.
Entities in DBMS are of various types, distinguished based on their features and context. There are two main types of entity sets. (entity types in DBMS).
A strong entity is a type of entity in a DBMS that does not rely on other entities to be uniquely identified. There will always be a primary key for a strong entity. A strong entity set is a set that is made up of various strong entities. A strong entity is its ability to exist independently without any other entities.
Without any other entities, this entity can exist in a database relation. Additionally, a strong entity is a primary key or key property that aids in the unique identification of each instance of the entity. These entities exist in the real world and are represented as objects.
Let’s see some real-world examples to understand the strong entity.
For example, in the same school databases
Let’s take another example: Employee (entity).
In an employee database, suppose there is an entity called Employee, which consists of attributes such as e_id, e_name, e_phone, e_dept, etc. Now, to uniquely identify an employee, the primary key, which is “e_id” in this example, can be used.
A weak entity set is a collection of entities that cannot exist independently without being linked to a stronger entity. As a strong entity consisting of a primary key, the weak entity has no primary key. A weak entity set is also known as a dependent entity in a DBMS. A weak entity takes the help of a strong entity and relies on a concept called a foreign key relationship.
It uses a strong entity and concept known as a foreign key connection to guarantee its uniqueness. Additionally, this entity in the database represents a part or component of the strong entity in the database.
Let’s see some real-world examples to understand the weak entity.
Order: In a customer_order database, suppose there is an entity called order that consists of different attributes, including order_id, email_date, email_sender, email_receiver, etc. Here, the email_id is dependent on the person_id, which is part of a strong entity called “Person” in a database.
You are aware of how important it is to group related elements if you have ever worked with databases. An entity set in a database management system is just that: a group of entities with similar features. It permits you to manage data more efficiently by grouping entities with the same structure. This is needed for database applications that involve large volumes of related data.
Let’s see an example of a “student.”
Thus, to define an entity set effectively, you need three key elements.
By organizing entities into sets, you can create a structured database architecture that is simpler to query, update, and manage. Let’s explore the specific terms you require to understand entity sets fully.
When working with entities set in a DBMS, you’ll encounter different key terms that describe how they function.
Having already gone through the types of entities, let us get familiar with the kinds of entities in DBMS. In this section, we will discuss the kinds of entities in DBMS. There are two main types of entities, tangible and intangible entities, in a DBMS, and why they’re crucial for any database.
A tangible entity is a physical object or a physical thing that can be physically touched, seen, or measured. Examples of tangible entities include a car, a laptop, a book, or even a person. These are examples of tangible entities that can be directly observed and measured.
Tangible entities are vital because they let you track physical aspects of a system, such as inventory or personnel. They’re often the beginning point for building the database because they’re easy to identify.
An intangible entity is an entity that does not exist in the physical world and cannot be touched. However, it is still dealing with them regularly, like a bank transaction, a loan, product categories, etc., as they do not exist physically and can’t be touched either, but are needed for various purposes.
Intangible entities are essential because they represent the actions, events, and concepts driving your database. Without them, you’d lose the logical structure that concepts and tangible entities have.
So, next time you come across terminology like entity in DBMS, think of tangible and intangible entities working together to bring data to life. Next, let’s understand the difference between an entity and an entity set in a DBMS.
When you understand the meaning, types of entity, and entity set, it's essential to know the difference between them. Think of it as the difference between a single student and a school and an entire class.
Attributes are the essential characteristics of entities that help those instances provide important information about themselves. Attributes are utilized to distinguish one entity from another. Attributes help to categorize the entity, and the entity can be easily retrieved and manipulated. There are various types of attributes of an entity that include
There are eight types of attributes in DBMS.
Simple attributes are those attributes that cannot be divided into more attributes. Simple attributes are also known as atomic attributes. Simple attributes state the simple information about the entity, such as name, roll_no, class, age, etc. Simple attributes are widely used for storing information about the entity.
Example: Student has roll number, section, and name as attributes that cannot be divided into more sub-attributes. This type is known as a simple attribute.
In simple terms, composite attributes are composed of one or more simple attributes. When two or more two simple attributes combine to make an attribute, then that attribute is called a composite attribute. Complex attributes are used where data is complex and required to be stored in a complex structure.
Example. As we can see in the above example, Address is a composite attribute represented, and it can be further divided into many simple attributes like street, city, state, country, landmark, etc. This type of attribute is known as a composite attribute.
Single-valued attributes are those attributes that consist of a single value for each entity instance and can’t have more than one value. The value of these single-valued attributes always remains the same, just like the name of the person.
Example: In the below example, we know that the DOB attribute will have only one value. So, we can say that the DOB attribute is nothing but a single value attribute, and it cannot have multiple attributes. Her name and roll number will also have mostly one value only. It can be said that all three characteristics of the student are single-valued.
An attribute that can have multiple values is known as a multivalued attribute. It can also be said to have the opposite functionality to that of single-valued attributes. It does not have one value.
Example: Here, the student has an attribute named phone_number. One student can have a multivalued attribute. So we can say that a phone_number can have multiple attributes. Each student in the real world can provide more than one phone number, and therefore, we require these attributes to be multi-valued so that they can store multiple values at a time for the entity instance.
The attribute that has unique values for every row in the table is known as a key attribute. The key attribute plays a vital role in the database. The key attribute is having a unique characteristic of the entity that can be used to identify the entity uniquely.
Example. For students, we can identify every student with roll_no because each student will have a unique roll_no. Here, roll_no will be a key attribute for the student entity.
Derived attributes in DBMS are those attributes whose values can be derived from the values of other attributes. They are always dependent upon other attributes for their values. Derived attributes are not stored directly in the database. It is calculated by using the stored attributes in the database.
Example: here, the student has multiple attributes, including DOB and age. It is seen that age can be calculated with the help of the DOB attribute. So age is an attribute derived from an attribute name, DOB.
Values of a store attribute remain constant and fixed for an entity instance; then it is called a stored attribute. These attributes are used to store permanent information about an entity, which will remain constant throughout the lifetime of the entity.
Example: the student has 3 attributes as shown below. Here, the name and DOB will remain the same throughout his/her education. So the student has a fixed value attribute that will never change in the future. These attributes are known as stored attributes.
When multiple valued and composite attributes come together to form an attribute, then it is called a complex attribute. Complex attributes can have an unlimited number of sub-attributes.
Example here for the student, we created an attribute named contact_info, which is further divided into phone_number and address. The address is a composite attribute, which is further divided into simple attributes, and phone_no is a multivalued attribute.
An entity relationship diagram is a type of flowchart that illustrates how entities such as people, objects, or concepts relate to each other within a system. ER diagrams are used to design or debug relational databases in the field of software engineering.
Also known as ERD or ER models, they use a defined set of symbols, such as rectangles, diamonds, ovals, and connecting lines, to depict the interconnectedness of entities, relationships, and their attributes. Trying to understand a database just by reading tables and columns is like solving a puzzle without a picture to guide you.
The ER model is used to model the logical view of the system from a data perspective, which consists of these symbols.
ERDs are graphical representations that show how entities and their relationships are structured in a DBMS. One important element of ERD is cardinality, which refers to the number of instances of one entity set that can or must be associated with each instance of another entity set in a relationship.
When each entity in each entity set can take part only once in the relationship, the cardinality is One-to-One.
For example, let's assume that a male can marry one female and a female can marry one male. So this relationship will be one-to-one.
In one-to-many relationships, one entity in the first entity set can be related to multiple entities in the second set. Still, each entity in the second set is related to only one entity in the first set.
Example: One surgeon department can accommodate many doctors. So the cardinality will be 1 to M. It means one department has many doctors.
A many-to-one relationship occurs when many entities in one set are associated with a single entity in another set.
Example: Many employees work in one department.
When entities in all entity sets can take part more than once in the relationship, cardinality is many-to-many.
Example: In an e-commerce platform, customers can purchase multiple products that multiple customers can buy.
Entities and entity sets are fundamental concepts in database management systems (DBMS) used to organize and represent real-world objects and data. DBMS applications range from banking to education, guaranteeing the effective management of large amounts of data. Various applications of DBMS are crucial for database professionals and students alike.
In the railway reservation system framework, the information base is required to store the records or information of ticket appointments and the status of train arrivals. Additionally, the information base update helps people become aware of any delay or train that gets late.
Web-based shopping has become popular. Many people still prefer physical shopping. Not everybody shops online. Preferences vary by region, age and access. A customer places multiple orders; each order contains multiple products where entities like customers, orders, and products.
Big firms or organizations have various specialists or representatives working under them. They store data about workers' compensation and assessment and work with the assistance of an information base administration framework. You see, entities in DBMS empower businesses and systems to handle data efficiently, creating better experiences for both users and systems.
Imagine yourself creating databases or analyzing large, complicated data sets that form the backbone of a multinational corporation. Doesn’t it look exciting? To succeed in such tasks, it is necessary to learn DBMS concepts such as entities.
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The four primary types of Database Management systems are Hierarchical, Network, relational, and Object-oriented.
In DBMS, an entity is a core concept that represents any real-world object, concept, or person that can store data.
The features of DBMS are data modeling, data storage and retrieval, concurrency control, data integrity and security, and backup and recovery.
A tuple represents a single row in a table, consisting of a set of related data values that together form one record.
DBMS keys are used to specify identifying attributes in the rows of database tables so the data can be sorted and organized for use in applications.
Yes, a bank is considered a type of entity, specifically a financial entity.
