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What is Entity in DBMS? Types, Examples

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18th Apr, 2023
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What is Entity in DBMS? Types, Examples

Introduction to Entity in DBMS

Entities are vital components of a database management system (DBMS) and are stored in the computer system’s data software. They represent real-world objects and can be distinguished by their specific features. The DBMS safeguards information and extracts valuable insights through entities.

An entity plays a crucial role in designing and implementing a relational database providing an organised way to store and retrieve data. The Entity Relationship Diagram Model visually represents entity relationships using specialised symbols. It establishes a logical structure by combining entities, attributes, and relationships. 

For example, bank entity accounts consist of the bank account as the table or entity and the personal details as the rows, including account number, type and holder’s name.  

Entity and Entity Relationship Diagrams are managed and designed by software engineers in DBMS and are in high demand. Programs like upGrad’s Executive PG Programme in Software Development – Specialisation in Full Stack Development can help you further strengthen your understanding of DBMS. 

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Until then, keep reading to get your basics right!

Types of Entities in DBMS

There are two different entity types in DBMS which include : 

types of entity in dbms

Tangible Entity

Tangible Entities in DBMS are physical objects which can be seen, touched and measured. They are represented in the database by tables or other structures that correspond to these physical objects.

Intangible Entity 

In database management, intangible entities are nonphysical objects that cannot be seen, touched or measured. They exist conceptually or logically rather than in the physical world. Intangible entities in DBMS include various elements such as emotions, thoughts and memories. 

Basic Components of an Entity

The Database Management System manages and restores data as entities and attributes. These entities are divided into various components, including: 

  • Strong entity set: Strong Entity Set is an entity that has its own unique identifier, known as a primary key. They do not depend on other entities and can work independently. 
  • Weak entity set: Weak entity in DBMS is an entity which does not comprise a primary key and depends on another entity for its existence. 
  • Associative entities: Associative entities showcase various relationships between entities and are signified as tables with foreign keys. 
  • Subtype entities: Subtypes are used to represent specialised instances or variations of an entity. 

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Characteristics of an Entity in DBMS

There are several key components in an entity-relationship diagram that helps to plan out a potential database, including : 

  • Entity name: The entity name is a unique identifier given to each entity in the database. It is represented in rectangles in an entity-relationship diagram (ERD) and helps distinguish one entity from another. 
  • Attributes: Attributes are represented in oval shapes or ellipses and describe the characteristics of an entity. 
  • Primary key: Primary key is a unique identifier for every entity and aids in differentiating one instance of the entity from others in the database management system. 
  • Relationships: Relationship connections are represented by solid lines and showcase the associations between different entities in the database. Relationships can be either single or many and are represented by foreign keys in the tables that correspond to the entities.

Importance of Entity in Database Design

Entity incorporates attributes and various primary and secondary keys while designing database management system, including: 

  • Data integrity: Entities are crucial for maintaining data integrity by defining the structure and relationships and ensuring consistent and error-free data storage. 
  • Data retrieval: Entities can be used to manage, measure and retrieve data from the database software. There is a usage of queries in data retrieval to sort and extract aggregate information.  
  • Data security: Data security ensures the full safety of information stored in the database by customising entity permissions and safeguarding personal details from hackers.
  • Data relationships: Entities can connect through relationships and build connections between various information and data.

Relationship between Entities in DBMS

Entities lie at the epicentre of Database Management Systems, and there are various types of relationships, including:

  • One-to-One Relationship: A single record in one entity is conjoined with another record in another entity. For example, an individual’s phone number and personal details are associated with the same person.
  • One-to-Many Relationship: Each record in a single entity can be associated with many more records in another entity. For example, one customer has a single customer ID and name but has multiple orders.
  • Many-to-Many Relationship: In a DBMS, multiple records in one entity can be associated with multiple records in another. For example, students can enrol in multiple courses, each with multiple students.

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Cardinality and Degree of Entity Relationship in DBMS

  • Cardinality: Cardinality showcases the relationship of the information in two different entities and its occurrences. It creates links and connections between various entities in a structured form. 
  • Degree: The degree of relationship is the number of entities incorporated in a particular relationship of database software. It indicates the number of attributes or columns in a database table associated with the relationship.

The Concept of Primary Key in Entity

A primary key is a unique identifier allocated to single or multiple columns in a relational database table. It ensures the uniqueness and integrity of information within the database. 

The primary key is a fundamental tool for updating, searching, and deleting records in the database. It has several key features:

  • Unique – For each row of the table, the primary key’s value should be unique. The columns of the database management system cannot comprise duplicate values and aid in identifying uniquely. 
  • Non-null –  The primary key columns or the attributes cannot comprise null values and must contain a definite value. 
  • Minimal and Easy Access – The primary key must comprise a minimal number of attributes and should be easily accessible to all the database administrators operating the database software. 

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Understanding Secondary Keys in Entity

The secondary key, also known as the alternate key, is a single or multiple column in a database management system table. It is used for accessing and retrieving records and data, and it helps improve query performance by providing an index on the specified columns. There are several characteristics of Secondary Keys in entities which include: 

  • The secondary key detects rows and possesses duplicate values in a table. 
  • A secondary key is used to make indexes on columns of a table, cater to improving performance, and aid in optimising query performances. 
  • Unlike a primary key, a secondary key can be null, and a single or more secondary key can be used. 

Creating Entities in DBMS

Several characteristics define what is entity in DBMS and how to create it: 

  • Click on System Administration and open the Manage Model page. 
  • Select the model template and click on Entities.
  • Click add on the Manage Entity box 
  • Select the Transaction Log Type in the Dropdown button and choose the Create Code values in the check box. 
  • Lastly, click the Enable Data Compression checkbox and click the Save button to restore. 

Curious about the foundational elements of database management? Learn about the types of keys in DBMS that play a crucial role in organizing, accessing, and maintaining data efficiently.

Examples of Entities in DBMS

Various examples define entity in DBMS and entity meaning in DBMS

  • An entity of  “Professor” has attributes such as Professor_ID number, Professor_name and

Professor_department. 

  • An entity of  “Teacher” has attributes such as Teacher_Name, Teacher_Address, Teacher_Salary. 
  • An entity to “Student” has attributes such as Student_Name, Student_Address, Student_Course. 
  • An entity of “Customer” has attributes such as Customer_Name, Customer_Product ID and Customer_Address. 
  • An entity of “Employee” has attributes such as Employee_Name, Employee_ID number and Employee_salary. 

Advantages of Entities in DBMS

There are various advantages of entities and attributes that showcase the entity relationship model in DBMS and define what is entity in database. 

  • Simple and Effective: Designing ER diagrams and an effective communication tool for data administrators is simple.
  • Provides Visual starting point: ER models offer a visual starting point for database software which aids in determining data system necessities in an enterprise. 
  • Integration and Conversion: The entities can be integrated with relational models and transformed into other models. 

Disadvantages of Entities in DBMS

The disadvantages of entities in DBMS include: 

  • Limited Relationship and Data Inconsistency: Entities can have limited relationships and may not always provide primary and secondary keys. Data inconsistency can also occur during the creation of entity diagrams in the database. 
  • Loss of data and Cardinalities: Sometimes, the data and entities get lost or hidden along with the cardinalities in the database. 
  • No Data Manipulation Language and Standard Notations: There is no data manipulation language and standard notations in an E-R model. 

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Challenges of Working with Entities in DBMS

The challenges of working with entities in DBMS include: 

  • Data quality and security issues: The foremost challenge while working with entities in DBMS is determining data accuracy and protecting sensitive data from hackers and unauthorised access. 
  • Scalability and Performance Issues: In the entity data model, as the information increases, it becomes difficult to scale up and manage entities, leading to a decrease in the performance of the software. 

Tips for Efficient Entity Management in DBMS

The suggestions for efficient entity management in database management systems include: 

  • Improve Data Integrity and Reduce Inconsistencies: Using ER models ensures data integrity by defining entity structure and relationships, reducing redundancy and inconsistency risks.
  • Use Indexes and Constraints: Utilise indexes and constraints (primary, secondary, foreign keys) to enhance query performance and ensure accurate information in database software. 
  • Use Protection Measures: Use protection measures to ensure data security and create passwords, encryption, and firewalls to deny access to hackers. 

Conclusion 

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Entity relations are the most fundamental building blocks of DBMS across the globe, from library catalogues to shipping inventories. They aid in modelling and managing business data, employee data, client information and personal records, including IP addresses and phone numbers. 

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Pavan Vadapalli

Blog Author
Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working on solving problems of scale and long term technology strategy.

Frequently Asked Questions (FAQs)

1Can the primary key be NULL?

In a Database Management System, a primary key cannot be null, and the columns need to contain a definite value.

2How to identify a strong entity and the relationship between two strong entities?

A strong entity is depicted as a single rectangle, and a single diamond represents the relationship between the two strong entities.

3What is an entity in SQL with an example?

In SQL, an entity is a table that collects and restores information. An entity is an object stored in Master Data Services models and contains members, which are the rows of master data.