ER Diagrams for Database Assignments — Free Tool for CS Students

Database courses require ER diagrams for assignments — usually a schema design for a management system (library, hospital, university, bank). This guide covers how to create a clean, professional ER diagram for your assignment using a free browser tool, how to match the notation your professor expects, and a set of complete ready-to-edit templates for the most common assignment types.

Crow's Foot vs Chen Notation — Which Does Your Assignment Require?

Before starting, check which ER notation your course uses. Most database textbooks and courses use one of two notations:

Notation	Look	Relationships shown as	Used in
Crow's Foot	Line ends look like crow's feet (three lines = many)	Lines between rectangles with crow's foot symbols at ends	Industry, modern tools, most online ERD tools
Chen Notation	Rectangles (entities), diamonds (relationships), ovals (attributes)	Diamond shapes between entity boxes	Older textbooks, many university courses

If your assignment requires Chen notation: Use ERDPlus (erdplus.com) — it is the best free tool for Chen notation with proper diamonds. The free ERD maker and most online tools use crow's foot only.

If your assignment uses crow's foot notation (or if notation is not specified): The free ERD maker and any Mermaid-based tool will work perfectly. Crow's foot is the industry standard used by professional database designers.

Assignment Templates — Common Database Scenarios

These are the most frequently assigned database scenarios in DBMS courses. Each is a complete Mermaid erDiagram you can paste and render:

College Management System:

erDiagram
    STUDENTS {
        int student_id PK
        string first_name
        string last_name
        date date_of_birth
        string email
        int department_id FK
        date enrollment_date
    }
    COURSES {
        int course_id PK
        string course_code
        string title
        int credits
        int department_id FK
    }
    DEPARTMENTS {
        int dept_id PK
        string name
        string head_of_dept
    }
    FACULTY {
        int faculty_id PK
        string name
        int dept_id FK
        string designation
    }
    ENROLLMENTS {
        int enrollment_id PK
        int student_id FK
        int course_id FK
        int semester
        string grade
    }
    TEACHES {
        int faculty_id FK
        int course_id FK
        int semester
    }

    STUDENTS ||--|| DEPARTMENTS : "enrolled in"
    STUDENTS ||--o{ ENROLLMENTS : "registers for"
    COURSES ||--o{ ENROLLMENTS : "has"
    DEPARTMENTS ||--o{ COURSES : "offers"
    DEPARTMENTS ||--o{ FACULTY : "employs"
    FACULTY ||--o{ TEACHES : "teaches"
    COURSES ||--o{ TEACHES : "taught by"

Bank Database System:

erDiagram
    CUSTOMERS {
        int customer_id PK
        string name
        string address
        string phone
        string email
        date date_of_birth
    }
    ACCOUNTS {
        int account_id PK
        int customer_id FK
        int branch_id FK
        string account_type
        decimal balance
        date opened_date
        string status
    }
    BRANCHES {
        int branch_id PK
        string name
        string address
        string city
    }
    TRANSACTIONS {
        int transaction_id PK
        int account_id FK
        string type
        decimal amount
        datetime transaction_date
        string description
    }
    LOANS {
        int loan_id PK
        int customer_id FK
        int branch_id FK
        decimal amount
        decimal interest_rate
        date start_date
        date end_date
        string status
    }

    CUSTOMERS ||--o{ ACCOUNTS : "holds"
    ACCOUNTS ||--|| BRANCHES : "maintained at"
    ACCOUNTS ||--o{ TRANSACTIONS : "records"
    CUSTOMERS ||--o{ LOANS : "takes"
    LOANS ||--|| BRANCHES : "issued by"

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How to Submit Your ERD for an Assignment

Once your ER diagram is ready, export it for submission:

1. Click Export PNG in the ERD maker toolbar. The PNG is saved to your Downloads folder at 2x resolution — sharp enough for print and screen.
2. Or click Export SVG if you need a scalable format that your professor can open in Inkscape or a browser.
3. Attach to your submission. Most assignment portals (Canvas, Blackboard, Moodle, Google Classroom) accept PNG image attachments directly.
4. If a document is required: Paste the PNG into a Word document or Google Doc alongside your written analysis.
5. Save the code too. Copy the Mermaid code to a text file and save it — if you need to revise the diagram after feedback, you can edit the code and re-export rather than rebuilding from scratch.

Before submitting, verify:

• All required entities are present and correctly named
• Relationship cardinalities (one-to-many, etc.) are marked correctly
• Primary and foreign keys are labeled
• The diagram is readable at the image resolution you are submitting

Common Student ERD Mistakes

These are the most common errors in student ER diagram assignments — check each before submitting:

Mistake	Description	How to fix
Missing primary keys	Not labeling which column is the PK	Add PK label after the column that uniquely identifies each record
Wrong cardinality	Marking a one-to-many as one-to-one	Think about it logically: one customer CAN HAVE MANY orders (one-to-many). One order has EXACTLY ONE customer (many-to-one from the other side)
Missing foreign keys	Not showing how tables connect	Every relationship line should correspond to a FK column in one of the entities
Attributes on relationships	Not modeling junction tables for M:N relationships	Many-to-many relationships often need a junction/bridge table (like ENROLLMENTS connecting STUDENTS and COURSES)
Too many or too few entities	Missing entities or over-engineering the schema	Re-read the assignment requirements and check every noun — nouns are usually entities
Unclear relationship labels	Not labeling what the relationship means	Add a verb phrase as the relationship label ("places", "belongs to", "contains")

Answering Specific Assignment Questions

Some assignment questions ask you to "draw an ER diagram" for a specific scenario. Here is the approach to translate a scenario description into a diagram:

1. Identify entities: Look for nouns in the description — Student, Course, Instructor, Department. Each becomes an entity (a table).
2. Identify attributes: What information do we need for each entity? Student has: name, student ID, date of birth, email. Each becomes a column.
3. Identify relationships: Look for verbs — "student enrolls in course", "instructor teaches course". Each verb describes a relationship between two entities.
4. Determine cardinality: Ask: "Can one [entity A] have multiple [entity B]? Can one [entity B] have multiple [entity A]?" This determines whether it is one-to-one, one-to-many, or many-to-many.
5. Handle many-to-many: If both answers to step 4 are "yes", you need a junction table. "Student enrolls in many courses, and each course has many students" → add an ENROLLMENTS table with student_id and course_id foreign keys.

Frequently Asked Questions

What ERD tool is best for DBMS assignments?

For crow's foot notation: the WildandFree free ERD maker, dbdiagram.io (requires free account), or draw.io. For Chen notation (with diamonds for relationships): ERDPlus is the best free option. Check with your professor which notation they expect before starting, since the tools produce different visual styles.

How do I create an ER diagram for a college management system?

A college management system ERD typically includes: STUDENTS, COURSES, DEPARTMENTS, FACULTY, and ENROLLMENTS entities. Students enroll in courses (many-to-many through ENROLLMENTS), departments offer courses (one-to-many), and faculty teach courses (many-to-many through a TEACHES junction table). The template earlier in this guide is a complete, ready-to-use version of this schema.

My professor wants the ER diagram in a specific format. Can I use this tool?

The free ERD maker produces PNG and SVG exports of crow's foot notation diagrams. If your professor requires a specific file format (like a Visio .vsdx file) or a specific notation style (like Chen notation), you may need a different tool. For most assignments asking for an "ER diagram as an image," the PNG export from this tool is universally accepted.

How many entities should a student ER diagram have?

It depends entirely on the assignment requirements. A simple library system might need 5-6 entities (BOOKS, AUTHORS, MEMBERS, LOANS, GENRES, BOOK_COPIES). A complex university management system might have 10-15. Focus on what the assignment describes, not on a number target. Every significant noun in the assignment requirements should typically be an entity.