An ER diagram in DBMS (database management systems) is a lot like a storyboard for an animated TV show – it’s a collection of diagrams that show how everything fits together. Where a storyboard demonstrates the flow from one scene to the next, an ER diagram highlights the components of your databases and the relationships they share.


Understanding the ER model in DBMS is the first step to getting to grips with basic database software (like Microsoft Access) and more complex database-centric programming languages, such as SQL. This article explores ER diagrams in detail.


ER Model in DBMS


An ER diagram in DBMS is a tangible representation of the tables in a database, the relationships between each of those tables, and the attributes of each table. These diagrams feature three core components:


  • Entities – Represented by rectangles in the diagram, entities are objects or concepts used throughout your database.
  • Attributes – These are the properties that each entity possesses. ER diagrams use ellipses to represent attributes, with the attributes themselves tending to be the fields in a table. For example, an entity for students in a school’s internal database may have attributes for student names, birthdays, and unique identification numbers.
  • Relationships – No entity in an ER diagram is an island, as each is linked to at least one other. These relationships can take multiple forms, with said relationships dictating the flow of information through the database.

Mapping out your proposed database using the ER model is essential because it gives you a visual representation of how the database works before you start coding or creating. Think of it like the blueprint you’d use to build a house, with that blueprint telling you where you need to lay every brick and fit every door.


Entities in DBMS


An Entity in DBMS tends to represent a real-life thing (like the students mentioned previously) that you can identify with certain types of data. Each entity is distinguishable from the others in your database, meaning you won’t have multiple entities listing student details.


Entities come in two flavors:


  • Tangible Entities – These are physical things that exist in the real world, such as a person, vehicle, or building.
  • Intangible Entities – If you can see and feel an entity, it’s intangible. Bank accounts are good examples. We know they exist (and have data attributed to them) but we can’t physically touch them.

There are also different entity strengths to consider:


  • Strong Entities – A strong entity is represented using a rectangle and will have at least one key attribute attached to it that allows you to identify it uniquely. In the student example we’ve already shared, a student’s ID number could be a unique identifier, creating a key attribute that leads to the “Student” entity being strong.
  • Weak Entities – Weak entities have no unique identifiers, meaning you can’t use them alone. Represented using double-outlined rectangles, these entities rely on the existence of strong entities to exist themselves. Think of it like the relationship between parent and child. A child can’t exist without a parent, in the same way that a weak entity can’t exist without a strong entity.

Once you’ve established what your entities are, you’ll gather each specific type of entity into an entity set. This set is like a table that contains the data for each entity in a uniform manner. Returning to the student example, any entity that has a student ID number, name, and birthdate, may be placed into an overarching “Student” entity set. They’re basically containers for specific entity types.



Attributes in DBMS


Every entity you establish has attributes attached to it, as you’ve already seen with the student example used previously. These attributes offer details about various aspects of the entity and come in four types:


  • Simple Attributes – A simple attribute is any attribute that you can’t break down into further categories. A student ID number is a good example, as this isn’t something you can expand upon.
  • Composite Attributes – Composite attributes are those that may have other attributes attached to them. If “Name” is one of your attributes, its composites could be “First Name,” “Surname,” “Maiden Name,” and “Nickname.”
  • Derived Attributes – If you can derive an attribute from another attribute, it falls into this category. For instance, you can use a student’s date of birth to derive their age and grade level. These attributes have dotted ellipses surrounding them.
  • Multi-valued Attributes – Represented by dual-ellipses, these attributes cover anything that can have multiple values. Phone numbers are good examples, as people can have several cell phone or landline numbers.

Attributes are important when creating an ER model in DBMS because they show you what types of data you’ll use to populate your entities.


Relationships in DBMS


As your database becomes more complex, you’ll create several entities and entity sets, with each having relationships with others. You represent these relationships using lines, creating a network of entities with line-based descriptions telling you how information flows between them.


There are three types of relationships for an ER diagram in DBMS:


  • One-to-One Relationships – You’ll use this relationship when one entity can only have one of another entity. For example, if a school issues ID cards to its students, it’s likely that each student can only have one card. Thus, you have a one-to-one relationship between the student and ID card entities.
  • One-to-Many Relationships – This relationship type is for when one entity can have several of another entity, but the relationship doesn’t work in reverse. Bank accounts are a good example, as a customer can have several bank accounts, but each account is only accessible to one customer.
  • Many-to-Many Relationships – You use these relationships to denote when two entities can have several of each other. Returning to the student example, a student will have multiple classes, with each class containing several students, creating a many-to-many relationship.

These relationships are further broken down into “relationship sets,” which bring together all of the entities that participate in the same type of relationship. These sets have three varieties:


  • Unary – Only one entity participates in the relationship.
  • Binary – Two entities are in the relationship, such as the student and course example mentioned earlier.
  • n-ary – Multiple entities participate in the relationship, with “n” being the number of entities.

Your ER diagram in DBMS needs relationships to show how each entity set relates to (and interacts with) the others in your diagram.


ER Diagram Notations


You’ll use various forms of notation to denote the entities, attributes, relationships, and the cardinality of those relationships in your ER diagram.


Entity Notations


Entities are denoted using rectangles around a word or phrase, with a solid rectangle meaning a strong entity and a double-outlined rectangle denoting a weak entity.


Attribute Notations


Ellipses are the shapes of choice for attributes, with the following uses for each attribute type:


  • Simple and Composite Attribute – Solid line ellipses
  • Derived Attribute – Dotted line ellipses
  • Multi-Valued Attribute – Double-lined ellipses

Relationship Notations


Relationship notation uses diamonds, with a solid line diamond depicting a relationship between two attributes. You may also find double-lined diamonds, which signify the relationship between a weak entity and the strong entity that owns it.


Cardinality and Modality Notations


These lines show you the maximum times an instance in one entity set can relate to the instances of another set, making them crucial for denoting the relationships inside your database.


The endpoint of the line tells you everything you need to know about cardinality and ordinality. For example, a line that ends with three lines (two going diagonally) signifies a “many” cardinality, while a line that concludes with a small vertical line signifies a “one” cardinality. Modality comes into play if there’s a minimum number of instances for an entity type. For example, a person can have many phone numbers but must have at least one.


Steps to Create an ER Diagram in DBMS


With the various notations for an ER diagram in DBMS explained, you can follow these steps to draw your own diagram:


  • Identify Entities – Every tangible and intangible object that relates to your database is an entity that you need to identify and define.
  • Identify Attributes – Each entity has a set of attributes (students have names, ID numbers, birthdates, etc.) that you must define.
  • Identify Relationships – Ask yourself how each entity set fits together to identify the relationships that exist between them.
  • Assign Cardinality and Modality – If you have an instance from Entity A, how many instances does it relate to in Entity B? Is there a minimum to consider? Assign cardinalities and modalities to offer the answers.
  • Finalize Your Diagram – Take a final pass over the diagram to ensure all required entities are present, they have the appropriate attributes, and that all relationships are defined.

Examples of ER Diagrams in DBMS


Once you understand the basics of the ER model in DBMS, you’ll see how they can apply to multiple scenarios:


  • University Databases – A university database will have entities such as “Student,” “Teacher,” “Course,” and “Class.” Attributes depend on the entity, with the people-based entities having attributes including names, dates of birth, and ID numbers. Relationships vary (i.e., a student may only have one teacher but a single teacher may have several students).
  • Hospital Management Databases – Entities for this type of database include people (“Patients,” “Doctors,” and “Nurses”), as well as other tangibles, such as different hospital buildings and inventory. These databases can get very complex, with multiple relationships linking the various people involved to different buildings, treatment areas, and inventory.
  • E-Commerce Databases – People play an important role in the entities for e-commerce sites, too, because every site needs a list of customers. Those customers have payment details and order histories, which are potential entities or attributes. Product lists and available inventory are also factors.

Master the ER Model in DBMS


An ER diagram in DBMS can look like a complicated mass of shapes and lines at first, making them feel impenetrable to those new to databases. But once you get to grips with what each type of shape and line represents, they become crucial tools to help you outline your databases before you start developing them.


Application of what you’ve learned is the key to success with ER diagrams (and any other topic), so take what you’ve learned here and start experimenting. Consider real-world scenarios (such as those introduced above) and draw diagrams based on the entities you believe apply to those scenarios. Build up from there to figure out the attributes and relationships between entity sets and you’re well on your way to a good ER diagram.

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The Value of Hackathons
OPIT - Open Institute of Technology
OPIT - Open Institute of Technology
Jan 5, 2026 6 min read

Bring talented tech experts together, set them a challenge, and give them a deadline. Then, let them loose and watch the magic happen. That, in a nutshell, is what hackathons are all about. They’re proven to be among the most productive tech events when it comes to solving problems and accelerating innovation.

What Is a Hackathon?

Put simply, a hackathon is a short-term event – often lasting just a couple of days, or sometimes even only a matter of hours – where tech experts come together to solve a specific problem or come up with ideas based on a central theme or topic. As an example, teams might be tasked with discovering a new way to use AI in marketing or to create an app aimed at improving student life.

The term combines the words “hack” and “marathon,” due to how participants (hackers or programmers) are encouraged to work around-the-clock to create a prototype, proof-of-concept, or new solution. It’s similar to how marathon runners are encouraged to keep running, putting their skills and endurance to the test in a race to the finish line.

The Benefits of Hackathons

Hackathons provide value both for the companies that organize them and the people who take part. Companies can use them to quickly discover new ideas or overcome challenges, for example, while participants can enjoy testing their skills, innovating, networking, and working either alone or as part of a larger team.

Benefits for Companies and Sponsors

Many of the world’s biggest brands have come to rely on hackathons as ways to drive innovation and uncover new products, services, and opportunities. Meta, for example, the brand behind Facebook, has organized dozens of hackathons, some of which have led to the development of well-known Facebook features, like the “Like” button. Here’s how hackathons help companies:

  • Accelerate Innovation: In fast-moving fields like technology, companies can’t always afford to spend months or years working on new products or features. They need to be able to solve problems quickly, and hackathons create the necessary conditions to deliver rapid success.
  • Employee Development: Leading companies like Meta have started to use annual hackathons as a way to not only test their workforce’s skills but to give employees opportunities to push themselves and broaden their skill sets.
  • Internal Networking: Hackathons also double up as networking events. They give employees from different teams, departments, or branches the chance to work with and learn from one another. This, in turn, can promote or reinforce team-oriented work cultures.
  • Talent Spotting: Talents sometimes go unnoticed, but hackathons give your workforce’s hidden gems a chance to shine. They’re terrific opportunities to see who your best problem solvers and most creative thinkers at.
  • Improving Reputation: Organizing regular hackathons helps set companies apart from their competitors, demonstrating their commitment to innovation and their willingness to embrace new ideas. If you want your brand to seem more forward-thinking and innovative, embracing hackathons is a great way to go about it.

Benefits for Participants

The hackers, developers, students, engineers, and other people who take part in hackathons arguably enjoy even bigger and better benefits than the businesses behind them. These events are often invaluable when it comes to upskilling, networking, and growing, both personally and professionally. Here are some of the main benefits for participants, explained:

  • Learning and Improvement: Hackathons are golden opportunities for participants to gain knowledge and skills. They essentially force people to work together, sharing ideas, contributing to the collective, and pushing their own boundaries in pursuit of a common goal.
  • Networking: While some hackathons are purely internal, others bring together different teams or groups of people from different schools, businesses, and places around the world. This can be wonderful for forming connections with like-minded individuals.
  • Sense of Pride: Everyone feels a sense of pride after accomplishing a project or achieving a goal, but this often comes at the end of weeks or months of effort. With hackathons, participants can enjoy that same satisfying feeling after just a few hours or a couple of days of hard work.
  • Testing Oneself: A hackathon is an amazing chance to put one’s skills to the test and see what one is truly capable of when given a set goal to aim for and a deadline to meet. Many participants are surprised to see how well they respond to these conditions.
  • Boosting Skills: Hackathons provide the necessary conditions to hone and improve a range of core soft skills, such as teamwork, communication, problem-solving, organization, and punctuality. By the end, participants often emerge with more confidence in their abilities.

Hackathons at OPIT

The Open Institute of Technology (OPIT) understands the unique value of hackathons and has played its part in sponsoring these kinds of events in the past. OPIT was one of the sponsors behind ESCPHackathon 6, for example, which involved 120 students given AI-related tasks, with mentorship and guidance from senior professionals and developers from established brands along the way.

Marco Fediuc, one of the participants, summed up the mood in his comments:

“The hackathon was a truly rewarding experience. I had the pleasure of meeting OPIT classmates and staff and getting to know them better, the chance to collaborate with brilliant minds, and the opportunity to take part in an exciting and fun event.

“Participating turned out to be very useful because I had the chance to work in a fast-paced, competitive environment, and it taught me what it means to stay calm and perform under pressure… To prospective Computer Science students, should a similar opportunity arise, I can clearly say: Don’t underestimate yourselves!”

The new year will also see the arrival of OPIT Hackathon 2026, giving more students the chance to test their skills, broaden their networks, and enjoy the one-of-a-kind experiences that these events never fail to deliver. This event is scheduled to be held February 13-15, 2026, and is open to all OPIT Bachelor’s and Master’s students, along with recent graduates. Interested parties have until February 1 to register.

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OPIT’s First Career Fair
OPIT - Open Institute of Technology
OPIT - Open Institute of Technology
Jan 5, 2026 6 min read

The Open Institute of Technology (OPIT) recently held its first-ever career fair to showcase its wide array of career education options and services. Representatives from numerous high-profile international companies were in attendance, and students enjoyed unprecedented opportunities to connect with business leaders, expand their professional networks, and pave the way for success in their future careers.

Here’s a look back at the event and how it ties into OPIT’s diverse scope of career services.

Introducing OPIT

For those who aren’t yet familiar, OPIT is an EU-accredited Higher Education Institution, offering online degrees in technological fields such as computer science, data science, artificial intelligence, cybersecurity, and digital business. Aimed at making high-level tech education accessible to all, OPIT has assembled a stellar team of tutors and experts to train the tech leaders of tomorrow.

The First OPIT Career Fair

OPIT’s first career fair was held on November 19 and 20. And as with OPIT’s lectures, it was an exclusively online event, which ensured that every attendee had equal access to key lectures and information. Interested potential students from all over the world were able to enjoy the same great experience, demonstrating a core principle that OPIT has championed from the very start – the principles of accessibility and the power of virtual learning.

More than a dozen leading international companies took part in the event, with the full guest list including representatives from:

  • Deloitte
  • Dylog Hitech
  • EDIST Engineering Srl
  • Tinexta Cyber
  • Datapizza
  • RWS Group
  • WE GRELE FRANCE
  • Avatar Investments
  • Planet Farms
  • Coolshop
  • Hoist Finance Italia
  • Gruppo Buffetti S.p.A
  • Nesperia Group
  • Fusion AI Labs
  • Intesi Group
  • Reply
  • Mindsight Ventures

This was a fascinating mix of established enterprises and emerging players. Deloitte, for example, is one of the largest professional services networks in the world in terms of both revenue and number of employees. Mindsight Ventures, meanwhile, is a newer but rapidly emerging name in the fields of AI and business intelligence.

The Response

The first OPIT career fair was a success, with many students in attendance expressing their joy at being able to connect with such a strong lineup of prospective employers.

OPIT Founder and Director Riccardo Ocleppo had this to say:

“I often say internally that our connection with companies – through masterclasses, thesis and capstone projects, and career opportunities – is the ‘cherry on the cake’ of the OPIT experience!

“It’s also a core part of our mission: making higher education more practical, more connected, and more aligned with what happens in the real world.

“Our first Career Fair says a lot about our commitment to building an end-to-end learning and professional growth experience for our community of students.

“Thank you to the Student and Career Services team, and to Stefania Tabi for making this possible.”

Representatives from some of the companies that attended also shared positive impressions of the event. A representative from Nesperia Group, for example, said:

“Nesperia Group would like to thank OPIT for the warm welcome we received during the OPIT Career Day. We were pleased to be part of the event because we met many talented young professionals. Their curiosity and their professional attitude really impressed us, and it’s clear that OPIT is doing an excellent job supporting their growth. We really believe that events like these are important because they can create a strong connection between companies and future professionals.”

The Future

Given the enormous success of the first OPIT career fair, it’s highly likely that students will be able to enjoy more events like this in the years to come. OPIT is clearly committed to making the most of its strong business connections and remarkable network to provide opportunities for growth, development, and employment, bringing students and businesses together.

Future events will continue to allow students to connect with some of the biggest businesses in the world, along with emerging names in the most exciting and innovative tech fields. This should allow OPIT graduates to enter the working world with strong networks and firm connections already established. That, in turn, should make it easier for them to access and enjoy a wealth of beneficial professional opportunities.

Given that OPIT also has partnerships in place with numerous other leading organizations, like Hype, AWS, and Accenture, the number and variety of the companies potentially making appearances at career fairs in the future should no doubt increase dramatically.

Other Career Services at OPIT

The career fair is just one of many ways in which OPIT leverages its company connections and offers professional opportunities and career support to its students. Other key career services include:

  • Career Coaching: Students are able to schedule one-on-one sessions with their own mentors and career advisors. They can receive feedback on their resumes, practice and improve their interview skills, or work on clear action plans that align with their exact professional goals.
  • Resource Hub: The OPIT Resource Hub is jam-packed with helpful guides and other resources to help students plan out and take smart steps in their professional endeavors. With detailed insights and practical tips, it can help tech graduates get off to the best possible start.
  • Career Events: The career fair is only one of several planned career-related events organized by OPIT. Other events are planned to give students the chance to learn from and engage with industry experts and leading tech firms, with workshops, career skills days, and more.
  • Internships: OPIT continues to support students after graduation, offering internship opportunities with leading tech firms around the world. These internships are invaluable for gaining experience and forging connections, setting graduates up for future success.
  • Peer Mentoring: OPIT also offers a peer mentoring program in which existing students can team up with OPIT alumni to enjoy the benefits of their experience and unique insights.

These services – combined with the recent career day – clearly demonstrate OPIT’s commitment to not merely educating the tech leaders of the future, but also to supporting their personal and professional development beyond the field of education, making it easier for them to enter the working world with strong connections and unrivaled opportunities.

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