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What is Entity in DBMS? Definition, Types and Examples

24th Apr, 2024
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    What is Entity in DBMS? Definition, Types and Examples

    When it comes to managing data, a database management system (DBMS) is a vital tool. But what is an entity? And why is it so important in a DBMS? Database management systems (DBMS) use entities to represent and manage data. An entity is an object that has a unique identity and can be manipulated as a single unit. In a DBMS, entities are usually organized into tables, which allow for more efficient storage and retrieval of data.

    In this detailed guide, I'll answer those questions and more, explaining everything you need to know about entities in DBMS. I'll also provide some examples to help you understand this fundamental concept. So whether you're new to database management or want to brush up on your knowledge, read on for an in-depth look at entities!

    What is an Entity in DBMS (Database Management)?

    In a database management system (DBMS), an entity is a piece of data tracked and stored by the system. This could be something as simple as a customer's name and address or more complex information such as an order or invoice. An entity is typically composed of multiple attributes, the individual data that make up the Entity.

    For example, a customer entity might have attributes such as first name, last name, and address. In some cases, an entity will also have relationships with other entities in the system. For example, a customer entity might be related to an order entity. Entity-relationship diagrams (ERDs) visualize the connections between entities in a DBMS. All in all, this is all you need to know about "what is an entity in database management".

    Types of Entity in DBMS

    There are two types of entity in database management: tangible and intangible. Here, we will explore both types of entities in greater detail so that you can better understand how they work in a DBMS.

    1. Tangible Entity with Example

    A tangible entity in database management is a physical object that can be touched, seen, or measured. For example, a table in a database is a tangible entity because it is an actual object that can be viewed and interacted with. Examples of tangible entities include cars, buildings, and people.

    2. Intangible Entity with Example

    An intangible entity in database management is a nonphysical object that cannot be touched, seen, or measured. For example, a user's login information (username and password) is an intangible entity in database management because it is not an actual object that can be viewed and interacted with. Intangible entities also include elements like thoughts, emotions, and memories.

    All in all, understanding the difference between these two entity types in DBMS is important for understanding how a DBMS works. Moreover, you can also get deep insights into the basics and working of database management with the Best MongoDB Course online and enhance your already diverse abilities.

    What is Entity Type in DBMS?

    An entity type in DBMS is a classification used to define and generate a set of entities that have common characteristics. For example, a company database may include entity types such as "customers," "products," and "sales." Each entity type in DBMS typically has its own set of attributes, or properties, that describe the Entity.

    In the customer example of Entity in database management, attributes might include name, address, and phone number. Entity types are often used to model real-world objects, such as people, places, and things. When designing a database, it is important to carefully consider which Entity types to include in order to ensure that the data model accurately represents the information that needs to be stored.

    Types of Entity Type
    types of entity type

    In a database management system (DBMS), an entity is a piece of data that is stored in the database. An entity can be a person, place, thing, or even an event. There are two types of entities in DBMS: strong and weak.  

    1. Strong Entity Type with Example

    A strong entity in DBMS is an independent table that doesn't rely on any other tables for its existence. A primary key uniquely identifies each row in the table, and foreign keys are used to relate this table to other tables. NULL values are not allowed in the primary key columns.  

    A simple example of a strong entity type would be "customer" in a customer relational database table. The customerID attribute would be the primary key (and it can't have duplicate values or be NULL), and other information about the customer would be stored in separate attributes such as "firstname," "last name," etc.

    2. Weak Entity Type with Example

    A weak entity type is a dependent table that relies on another table for its existence; it has no meaningful attributes of its own except for the foreign key from the parent table. For a weak entity type to exist, it must have some relationship with another (parent) table; otherwise, it wouldn't appear in the database!

    A typical example of a weak entity type is an "order." It has no meaning by itself–it must be placed by some customer so it has a foreign key relation to the "customer" table–but it has several attributes of its own such as orderID, productID, etc.  

    What is Entity Set in DBMS?

    In a database management system (DBMS), an entity set is a collection of similar entities. These can have attributes that specify them, and these attributes can be used to specify constraints or conditions. Entity sets are usually defined by a database administrator (DBA) or other IT staff. In some cases, entity sets may be generated automatically by the DBMS based on data in the database.

    Entity sets are used to model real-world objects, such as customers, products, or orders. They can also be used to model concepts, such as profit margins or customer satisfaction levels. Entity set definitions usually include a name and a description of the entities in the set. In some cases, they may also include attribute information or other details. Entity sets are used in many database applications, such as data mining, business intelligence, and decision support systems.

    They can also be used in transaction processing applications, such as order entry or inventory management. In each of these applications, entity sets provide a way to structure data and make it easier to understand and work with. 

    Terminologies Used in Entity Set

    Attributes are the houses or traits of an entity. They describe the data that may be connected with an entity
    Entity Instance
    An entity example is a particular incidence or character entity within an entity type.
    Each entity instance has a unique identity, often known as number one key.
    Entity Type
    A category or class of entities that share the same attributes is referred to as an entity kind.
    Primary Key
    It is a unique identifier for every entity instance inside an entity kind

    Types of Entity Set

    In a DBMS, data is stored as entities and attributes. These entities can be either strong or weak. We will discuss the different types of entity sets in greater detail.

    So, what is a weak Entity set in DBMS? Let us know.  

    1. Weak Entity Set in DBMS with Example

    A weak entity set is an entity that does not contain a primary key. This means that the Entity depends on another entity for its existence. For example, consider the following scenario:

    You are looking at a list of students and their grades. The problem is that some students do not have grades yet because they have not taken the course. These students without grades would be considered a weak entity set because they depend on another entity (in this case, a grade) for their existence.  

    2. Strong Entity Set in DBMS with Example

    A strong entity set in DBMS is an entity that has a primary key. This means the Entity does not need another entity to exist—it can stand alone. Continuing with the same example of Entity in database management from above:

    When you look at the list of students and their grades, you notice that all students have grades. Because each student has a unique identifier (primary key), they are considered part of a strong entity set in DBMS.

    Examples are just a layman's approach to understanding the Entity in DBMS, but you must look for a more professional approach to this type of learning in the best MongoDB course.  

    So, enroll in MongoDB DBA Online Training sessions and take their expertise to maximize your skills.  

    Difference Between an Entity and an Entity Set

    In a database, an entity is a piece of data that can be uniquely identified. An entity set is a grouping of entities that share the same attributes. In other words, an entity set is a group of distinct entities that have the same properties. For example, a customer entity might have the name, address, and phone number attributes. A customer entity set would then be a group of customers with those same attributes.

    Entity sets are used to organize data in a database. By grouping objects with the same attributes together, it becomes easier to query and manipulate the data. Additionally, separating different entity sets prevents data from becoming cluttered and disorganized. For example, if all customer data is stored in the same table as product data, it would be difficult to find specific information.

    However, storing customer information in its own table makes it much easier to retrieve and work with the data. In short, an entity is a single piece of data, while an entity set is a group of related entities. Entity sets are useful for organizing data in a database and make it easier to query and manipulate information.

    Entity Set
    A thing in the real world with independent existence
    Set of all entities of a particular entity type.
    Any particular row (a record) in a relation(table)
    All rows of a relation in RDBMS are entity set

    How to Create an Entity Relationship Diagram (ERD)?

    An Entity Relationship Diagram (ERD) is tool developers use to visually represent the relationships between various data pieces or entities in a database. To create an effective ERD, developers must first understand the relationships between the entities they are trying to represent. Once these relationships have been identified, developers can map out the ERD.

    Cardinality is the most important element of an ERD, which show one Entity is related to another. These lines can represent several types of relationships.

    entity relationship diagram

    • One-to-one (e.g., one customer has one account): A one-to-one relationship exists when there is only one record in one table that corresponds to only one record in another table. For example, let's say we have a table of customer information and a table of account information. Each customer can only have one account, and each account can only belong to one customer. Therefore, the customer and account tables relationship would be considered a one-to-one relationship.

    • One to Many (e.g., one customer has many orders): A one-to-many relationship is when one Entity can be related to multiple entities, but each Entity can only be related to one other Entity. For example, in a school database, each student can take multiple classes, but each class can only have one teacher. So the relationship between the entities "student" and "class" is one-to-many.

    • Many to Many ( e.g., multiple customers can buy multiple products): A many-to-many relationship is when multiple entities are related to multiple other entities. For example, think of customers and products. Multiple customers can buy multiple products, and multiple customers can buy multiple products.

    Other components involved in ERD are Entity and Attributes. Here are common symbols for different types of entities and attributes.

    ER diagram symbols

    In addition to relationship lines, ERDs also include entity boxes, which contain the attributes of each Entity. When creating an ERD, it is important to ensure that all entities and relationships are represented. Otherwise, the ERD will be ineffective at communicating the relationships between the data elements in a database. All in all, this is all about how to create ER diagram effectively.

    To get a more detailed approach to ERD and other related concepts, it is advisable to opt for the KnowledgeHut best MongoDB course and get your practical learning on board with industry experts and professionals. 


    An entity in DBMS can be a real-world object, either concrete or abstract, that can be identifiable. A set of attributes represents an entity. So we have seen that an entity in DBMS is a real-world object with some attributes defining it. And these entities are linked to each other via relationships. I hope you found this guide helpful. Do let me know your thoughts in the comments section below! 

    Frequently Asked Questions (FAQs)

    1How do you know if you have a weak entity set in DBMS?

    There are a few key indicators that you have a weak entity set in your DBMS. First, you'll likely have an attribute partially or fully dependent on another. For example, you might have an "ID" attribute that is dependent on a "Name" attribute. Secondly, you may have an attribute dependent on more than one attribute. This is known as a transitive dependency.

    Lastly, you may find that you have two or more attributes that are functionally dependent on each other. This is known as a recursive dependency. You likely have a weak entity set if you have any of these dependencies in your DBMS. 

    2What is the difference between weak and strong entity sets in DBMS?

    In a database management system (DBMS), an entity is a piece of data that a unique identifier can identify. A weak entity is one that cannot be uniquely identified by its attributes and must use the attributes of another entity, known as its owner, to be uniquely identified. On the other hand, a strong entity in DBMS can be uniquely identified by its own attributes.

    Generally, a strong entity has a primary key, while a weak entity does not. However, there are some exceptions to this rule. For example, a relationship between two entities can be considered a strong entity in DBMS if it has a primary key made up of the foreign keys of the participating entities.

    3What is an entity in SQL with an example?

    In SQL, an entity is a table that stores data. For example, a customer entity might store customer information, such as their name, address, and phone number. An entity can also be a view, which is a stored query that selects data from one or more tables. For example, a view could be created to select all customers from the customer entity who live in the same city.


    Abhresh Sugandhi


    Abhresh is specialized as a corporate trainer, He has a decade of experience in technical training blended with virtual webinars and instructor-led session created courses, tutorials, and articles for organizations. He is also the founder of Nikasio.com, which offers multiple services in technical training, project consulting, content development, etc.

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