In ECET 2026 CSE, questions from Database Management Systems (DBMS) are common and scoring. Among them, Entity-Relationship (E-R) diagrams are a fundamental topic. They help you visualize the structure of a database and understand relationships between data. This topic often appears in MCQ form, and mastering it will strengthen your core DBMS knowledge while boosting your ECET score.
📘 Concept Notes – E-R Diagrams (Entity, Attributes)
🗂️ What is an E-R Diagram?
An Entity-Relationship Diagram (ERD) is a visual representation of data and the relationships between entities in a database. It was introduced by Peter Chen in 1976.
📍 Key Elements of an E-R Diagram:
- Entity
- An object that can be distinctly identified.
- Types:
- Strong Entity → Exists independently (e.g., Student, Employee).
- Weak Entity → Exists only with another entity (e.g., Dependent of Employee).
- Representation: Rectangle in E-R diagrams.
- Attributes
- Properties or characteristics of an entity.
- Types:
- Simple Attribute → Cannot be divided further (e.g., Name).
- Composite Attribute → Can be divided (e.g., Full Name → First Name + Last Name).
- Derived Attribute → Calculated from other attributes (e.g., Age from DOB).
- Multivalued Attribute → Can have multiple values (e.g., Phone Numbers).
- Representation: Oval shape connected to the entity.
- Relationships
- Association between entities (e.g., Student “enrolls in” Course).
- Cardinality: One-to-One, One-to-Many, Many-to-Many.
- Representation: Diamond shape.
💡 Example
- Entity: Student (Name, Roll No, DOB)
- Entity: Course (Course ID, Name)
- Relationship: Enrolls (between Student and Course)
🔟 10 Most Expected MCQs – ECET 2026 [E-R Diagrams]
Q1. In an E-R diagram, entities are represented by:
A) Ovals
B) Rectangles
C) Diamonds
D) Circles
Q2. Which of the following is a property of an entity?
A) Relation
B) Attribute
C) Record
D) Tuple
Q3. Which symbol represents a relationship in an E-R diagram?
A) Rectangle
B) Oval
C) Diamond
D) Line
Q4. Which of the following is a derived attribute?
A) Age
B) Name
C) Roll No
D) Address
Q5. A weak entity:
A) Exists independently
B) Needs a strong entity to exist
C) Cannot have attributes
D) Has no relationships
Q6. Multivalued attributes are represented by:
A) Dashed ovals
B) Double ovals
C) Double rectangles
D) Diamonds
Q7. Composite attribute means:
A) Attribute with multiple values
B) Attribute that can be split into sub-parts
C) Attribute derived from another
D) Attribute without a value
Q8. In ER diagrams, which is NOT an attribute type?
A) Derived
B) Multivalued
C) Composite
D) Transaction
Q9. The relationship between Employee and Department in “Employee works in Department” is:
A) One-to-Many
B) Many-to-One
C) Many-to-Many
D) One-to-One
Q10. The person who introduced E-R model is:
A) Edgar Codd
B) Peter Chen
C) Charles Bachman
D) Bill Inmon
✅ Answer Key Table
| Q.No | Answer |
|---|---|
| Q1 | B |
| Q2 | B |
| Q3 | C |
| Q4 | A |
| Q5 | B |
| Q6 | B |
| Q7 | B |
| Q8 | D |
| Q9 | A |
| Q10 | B |
🧠 Explanations of All Answers
- Q1 → B: Rectangles represent entities in ER diagrams.
- Q2 → B: Attributes describe the properties of entities.
- Q3 → C: Diamonds are used for relationships.
- Q4 → A: Age is calculated from Date of Birth (derived).
- Q5 → B: Weak entities require a strong entity to exist.
- Q6 → B: Multivalued attributes use double ovals.
- Q7 → B: Composite attributes can be split into sub-attributes.
- Q8 → D: Transaction is not a valid attribute type.
- Q9 → A: One department can have many employees → One-to-Many.
- Q10 → B: Peter Chen proposed the ER model.
🎯 Why This Practice Matters for ECET 2026
E-R diagrams are simple to learn but appear in almost every ECET CSE paper. These questions are direct and visual, making them easy marks if you know the symbols and attribute types. Practicing MCQs on entities and attributes improves database design understanding and exam accuracy.
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