1. 1NF (First Normal Form)

Rule:

👉 A table is in 1NF if:

All values are atomic (single value per cell, no multiple values).
No repeating groups or arrays in a column.

Example (Not in 1NF ❌):

StudentID	Name	Subjects
1	John	Math, Science
2	Alice	Physics, Chem

Problem: Column Subjects has multiple values in one cell.

Fixed Table (In 1NF ✅):

StudentID	Name	Subject
1	John	Math
1	John	Science
2	Alice	Physics
2	Alice	Chem

Now → each cell has only one value.

✅ Super Simple Definition:

👉 1NF = No repeating groups + Atomic values (one value per cell).

2. 2NF (Second Normal Form)

Step 1: Recall 1NF (First Normal Form)

Table must have atomic values (no repeating groups, no multiple values in one cell).
✔️ Example (Good 1NF):

StudentID	Subject	Marks
1	Math	90
1	Science	85
2	Math	88

Step 2: What is 2NF?

A table is in 2NF if:

It is already in 1NF ✅
Each non-key column must depend on the entire primary key — not only a part of it.

👉 This problem occurs only when you have a composite key (primary key made of 2+ columns).

Step 3: Example (Not in 2NF)

StudentID	Subject	StudentName	Marks
1	Math	John	90
1	Science	John	85
2	Math	Alice	88

Here, Primary Key = (StudentID, Subject)
Problem ❌: StudentName depends only on StudentID, not on both (StudentID + Subject).
This is called partial dependency.

Step 4: Fix it → Convert to 2NF

👉 Split the table into two:

Table 1: Student

StudentID	StudentName
1	John
2	Alice

Table 2: Marks

StudentID	Subject	Marks
1	Math	90
1	Science	85
2	Math	88

Now ✅ every column depends on the whole primary key.

✅ Super Simple Definition:

👉 2NF = 1NF + No partial dependency
(Every non-key column must depend on the whole primary key, not just a part of it).

3. 3NF (Third Normal Form)

Step 1: Recall 2NF

Table is in 2NF if there are no partial dependencies (non-key columns depend on the whole primary key).

Step 2: What is 3NF?

A table is in 3NF if:

It is already in 2NF ✅
No transitive dependency exists.

👉A column depends on another column instead of depending directly on the key.

Step 3: Example (Not in 3NF)

StudentID	StudentName	DepartmentID	DepartmentName
1	John	D1	Computer Sci
2	Alice	D2	Physics

Primary Key = StudentID
Problem ❌: DepartmentName depends on DepartmentID, which itself depends on StudentID.
So DepartmentName is indirectly dependent on StudentID.
This is a transitive dependency.

Step 4: Fix it → Convert to 3NF

👉 Break into two tables:

Table 1: Students

StudentID	StudentName	DepartmentID
1	John	D1
2	Alice	D2

Table 2: Departments

DepartmentID	DepartmentName
D1	Computer Sci
D2	Physics

Now ✅ all non-key columns depend directly on the primary key only.

✅ Super Simple Definition:

👉 3NF = 2NF + No transitive dependency
(Every non-key column must depend only on the primary key, not on other non-key columns).

4. BCNF (Boyce-Codd Normal Form)

Step 1: Recall 3NF

A table is in 3NF if it’s in 2NF and has no transitive dependency (A column depends on another column, not directly on the key).
But sometimes 3NF still allows problems when there are multiple candidate keys.

Step 2: What is BCNF?

A table is in BCNF if:
👉 For every functional dependency (X → Y), X must be a super key.

In simple words:
✅ Every determinant (the thing on the left side) must be a key.

Step 3: Example (Not in BCNF)

StudentID	Course	Instructor
1	DBMS	Prof. A
2	Networks	Prof. B
3	DBMS	Prof. A

Candidate Keys: (StudentID, Course) and (Course, Instructor)
Functional Dependencies:
- StudentID + Course → Instructor ✅ (OK, left side is key)
- Course → Instructor ❌ (Here, Course is not a key, but it determines Instructor).

So table violates BCNF.

Step 4: Fix it → Convert to BCNF

Split into two tables:

Table 1: Course_Instructor

Course	Instructor
DBMS	Prof. A
Networks	Prof. B

Table 2: Student_Course

StudentID	Course
1	DBMS
2	Networks
3	DBMS

Now ✅ every dependency has a key on the left side.

✅ Super Simple Definition:

👉 BCNF = Stronger 3NF

3NF removes transitive dependency.
BCNF goes further: Every determinant must be a candidate key.

Key Differences:

Normal Form	Goal	Key Points
1NF	Eliminate *duplicate data*, single values per column	Unique rows, atomic values
2NF	Eliminate *partial dependency*	No partial dependency on primary key
3NF	Eliminate *transitive dependency*	No non-key attribute depends on another non-key attribute
BCNF	Left side of the dependency must be a superkey	Left side of dependency must be a superkey

Quick Tips to Remember:

1NF: Atomic values (no lists).
2NF: No partial dependency (whole primary key).
3NF: No transitive dependency (non-key attributes don’t depend on each other).
BCNF: Every dependency must have a superkey on the left side.

✅ MCQs on NORMAL FORMS

1. Which of the following is required for a relation to be in 1NF?

A. No partial dependency
B. No transitive dependency
C. Atomic values only
D. No multivalued dependency

✔ Answer: C

2. A table violates 1NF when it contains:

A. Null values
B. Composite primary key
C. Repeating groups / non-atomic attributes
D. No foreign key

✔ Answer: C

3. A relation is in 2NF if it is in 1NF and:

A. Has no transitive dependency
B. Has no partial dependency
C. Has no multi-valued dependency
D. Has no functional dependency

✔ Answer: B

4. Partial dependency occurs when:

A. A non-key attribute depends on part of a composite key
B. A non-key attribute depends on the whole key
C. Two non-key attributes depend on each other
D. None

✔ Answer: A

5. A relation is in 3NF if it is in 2NF and:

A. Every non-key attribute depends only on candidate key
B. There is no partial dependency
C. There is no multi-valued dependency
D. Primary key exists

✔ Answer: A

6. Transitive dependency means:

A. A → B and B → C implies A → C
B. A non-key → key
C. Key → key
D. None

✔ Answer: A

7. A table in BCNF must be in:

A. 1NF only
B. 2NF only
C. 3NF and every determinant must be a candidate key
D. 4NF

✔ Answer: C

8. Which normal form eliminates all functional dependency anomalies?

A. 2NF
B. 3NF
C. BCNF
D. 4NF

✔ Answer: C

**9. The highest normal form based on functional dependencies only is:**

A. 3NF
B. BCNF
C. 4NF
D. 5NF

✔ Answer: B

10. A multi-valued dependency exists when:

A. One attribute determines multiple independent values of another
B. Two attributes depend on each other
C. Transitive dependency exists
D. None

✔ Answer: A

11. A relation is in 4NF if it is in BCNF and:

A. Contains no transitive dependency
B. Contains no multi-valued dependency
C. Contains no join dependency
D. Contains no partial dependency

✔ Answer: B

12. 5NF deals with

A. Join dependencies
B. Partial dependencies
C. Transitive dependencies
D. Multi-valued dependencies

✔ Answer: A

13. The process of converting an ER model to tables is called:

A. Structuring
B. Schema refinement
C. Normalization
D. Optimization

✔ Answer: C

14. Normalization is used to:

A. Reduce data anomalies
B. Increase redundancy
C. Slow down query performance
D. Remove candidate keys

✔ Answer: A

15. Update anomalies occur due to:

A. Fully normalized table
B. Redundant data
C. Foreign key violations
D. Schema constraints

✔ Answer: B

16. Which anomaly is removed by 1NF?

A. Update anomaly
B. Insertion anomaly
C. Repeating group anomaly
D. Deletion anomaly

✔ Answer: C

17. Which normal form removes partial dependencies?

A. 1NF
B. 2NF
C. 3NF
D. BCNF

✔ Answer: B

18. Which normal form ensures no transitive dependency?

A. 1NF
B. 2NF
C. 3NF
D. 5NF

✔ Answer: C

19. BCNF is stronger than 3NF because:

A. It removes all anomalies
B. It requires each determinant to be a candidate key
C. It requires atomic values
D. It is required for distributed DBMS

✔ Answer: B

20. A table is in BCNF but not in 4NF when:

A. It contains multi-valued dependencies
B. It contains transitive dependencies
C. It has composite keys
D. It has no primary key

✔ Answer: A

21. Normalization helps in:

A. Minimizing redundancy
B. Maximizing redundancy
C. Increasing anomalies
D. Slowing database operations

✔ Answer: A

22. The condition for 3NF is:

A. X → Y and X must be a superkey
B. Y must be a prime attribute or X must be a superkey
C. No multi-valued dependency
D. No join dependency

✔ Answer: B

23. Functional dependencies are used in determining:

A. Keys
B. Normal forms
C. Anomalies
D. All of the above

✔ Answer: D

24. If a relation has only single candidate key, BCNF and 3NF:

A. Are always identical
B. Are always different
C. Cannot be determined
D. BCNF does not apply

✔ Answer: A

25. Which of the following is NOT true about normalization?

A. It reduces redundancy
B. It improves consistency
C. It makes schema rigid
D. It removes anomalies

✔ Answer: C

26. The decomposition is lossless when:

A. Common attribute is a superkey in one of the decomposed relations
B. All attributes are atomic
C. All dependencies are preserved
D. Table size increases

✔ Answer: A

27. Dependency preservation means:

A. All original FDs can be derived after decomposition
B. No data loss
C. No multivalued dependency
D. No repeated values

✔ Answer: A

28. Which normal form is based on multivalued dependency?

A. 3NF
B. BCNF
C. 4NF
D. 5NF

✔ Answer: C

29. Which normal form is based on join dependency?

A. 4NF
B. 5NF
C. BCNF
D. 2NF

✔ Answer: B

30. A table is considered normalized when it is at least:

A. 1NF
B. 2NF
C. 3NF
D. 4NF

✔ Answer: C

This is because 3NF eliminates most practical anomalies.

🚀 TOP 40 MOST IMPORTANT MCQs ON NORMAL FORMS

1. Which of the following is removed by 1NF?

A. Partial dependency
B. Transitive dependency
C. Repeating groups
D. Multi-valued dependency
✔ Ans: C

2. 2NF removes which type of dependency?

A. Multi-valued dependency
B. Transitive dependency
C. Partial dependency
D. Key dependency
✔ Ans: C

3. A table is in 3NF if:

A. It has no partial dependency
B. It has no transitive dependency
C. It has atomic values
D. It has only a single candidate key
✔ Ans: B

4. BCNF is stricter than 3NF because:

A. Every determinant must be a candidate key
B. Atomic values are mandatory
C. Primary key must be composite
D. Only one candidate key allowed
✔ Ans: A

5. A transitive dependency exists when:

A. A → B and B → C
B. A → C only
C. Key → non-key
D. Non-key → key
✔ Ans: A

6. Which normal form deals with multi-valued dependency?

A. 2NF
B. 3NF
C. BCNF
D. 4NF
✔ Ans: D

7. Join dependency is handled in:

A. 4NF
B. 5NF
C. BCNF
D. 2NF
✔ Ans: B

8. A decomposition is lossless if:

A. All dependencies are preserved
B. Shared attribute is a superkey
C. No partial dependency
D. All attributes are atomic
✔ Ans: B

9. 3NF allows which dependency that BCNF does NOT?

A. Partial dependency
B. Transitive dependency
C. Dependency where determinant is a prime attribute
D. Multi-valued dependency
✔ Ans: C

10. Which best describes normalization?

A. Reducing redundancy and anomalies
B. Increasing redundancy
C. Improving storage
D. Improving indexing
✔ Ans: A

11. Update anomalies are caused due to:

A. Lack of indexes
B. Data redundancy
C. No primary key
D. Stored procedures
✔ Ans: B

12. A relation is in BCNF if:

A. It is in 3NF and non-key attributes depend on key
B. Every determinant is a candidate key
C. It has a single key
D. No multi-valued dependency
✔ Ans: B

13. Which normal form is based on only functional dependencies?

A. 2NF
B. 3NF
C. BCNF
D. 4NF
✔ Ans: C

14. Partial dependency occurs when:

A. Non-key attribute depends on part of composite key
B. Key → key
C. Non-key depends on non-key
D. Composite key depends on attribute
✔ Ans: A

15. Transitive dependency is allowed in:

A. 3NF
B. 2NF
C. BCNF
D. 1NF
✔ Ans: D

16. Most real-world databases use which normal form?

A. 1NF
B. 2NF
C. 3NF
D. BCNF
✔ Ans: C

17. Functional dependencies help in:

A. Identifying candidate keys
B. Determining normal forms
C. Designing schema
D. All of the above
✔ Ans: D

**18. Which NF eliminates transitive dependencies?**

A. 2NF
B. 3NF
C. 4NF
D. BCNF
✔ Ans: B

19. A relation with multi-valued dependency but no functional dependency violation belongs to:

A. 2NF
B. 3NF
C. BCNF
D. 4NF
✔ Ans: C (BCNF satisfied), must go to 4NF to remove MVD.

20. Which normal form ensures no redundancy due to multiple independent attributes?

A. 2NF
B. 3NF
C. 4NF
D. 5NF
✔ Ans: C

21. In 3NF, a non-prime attribute:

A. Must depend on the whole key
B. Must not depend on another non-prime attribute
C. Must be atomic
D. Must be unique
✔ Ans: B

22. A table has attributes A, B, C. If A → B and B → C, then A → C is:

A. Partial dependency
B. Transitive dependency
C. Multi-valued dependency
D. Join dependency
✔ Ans: B

23. Which normal form eliminates the possibility of insertion anomalies due to repeating groups?

A. 1NF
B. 2NF
C. 3NF
D. 4NF
✔ Ans: A

24. 5NF is mainly concerned with

A. Key dependency
B. Join dependency
C. Partial dependency
D. Transitive dependency
✔ Ans: B

25. BCNF is violated when:

A. Non-key attribute determines a key attribute
B. Composite key exists
C. Null values exist
D. Functional dependencies are missing
✔ Ans: A

26. A relation is in 2NF only if the primary key is:

A. Composite
B. Non-composite
C. Candidate key
D. Any key
✔ Ans: A (2NF only matters for composite keys)

27. 3NF does not allow:

A. Partial dependency
B. Transitive dependency
C. Atomic values
D. Candidate keys
✔ Ans: B

28. Which normal form is sometimes called “Elementary Key Normal Form”?

A. 3NF
B. BCNF
C. 5NF
D. 4NF
✔ Ans: C (5NF)

29. A decomposition is dependency-preserving if:

A. All functional dependencies can be inferred after decomposition
B. No repeating groups
C. No join required
D. All values are atomic
✔ Ans: A

30. Lossless join and dependency preservation cannot always be achieved together in:

A. 2NF
B. 3NF
C. BCNF
D. 5NF
✔ Ans: C

⭐ BONUS: High-Probability Case-Based Questions (Most Asked)

31. A table Student(ID, Course, Instructor) has:

ID → Instructor
Course → Instructor

Which NF is violated?
A. 2NF
B. 3NF
C. BCNF
D. 4NF
✔ Ans: C (Instructor is determined by Course which is not candidate key)

**32. Employee(EmpID, Dept, Manager)

FDs: Dept → Manager
Key: EmpID**

Which is TRUE?
A. Table is in BCNF
B. BCNF violated
C. 3NF violated
D. 2NF violated
✔ Ans: B (Dept is not a key but determines Manager)

**33. R(A,B,C)

FDs: A → B
Key = A
Then R is in:**
A. 1NF only
B. 2NF only
C. 3NF and BCNF
D. Only 3NF
✔ Ans: C

34. Given composite key (A, B):

Dependency A → C means:
A. Partial dependency exists
B. Transitive dependency exists
C. No dependency
D. Key is wrong
✔ Ans: A

35. Table: Order(OrderID, Product, Supplier, SupplierPhone)

FD: Supplier → SupplierPhone
Key: OrderID + Product

NF satisfied?
A. 1NF only
B. 2NF
C. 3NF violated
D. BCNF violated
✔ Ans: D (Supplier is not a key)

36. A table has more than one candidate key. 3NF = BCNF when:

A. All candidate keys are single-attribute
B. All FDs have determinant as candidate key
C. Composite keys exist
D. MVD exists
✔ Ans: A

37. 4NF removes anomalies caused by:

A. Functional dependency
B. Transitive dependency
C. Multi-valued dependency
D. Join dependency
✔ Ans: C

38. If FD is X → Y, then X is called:

A. Determinant
B. Dependent
C. Attribute set
D. None
✔ Ans: A

39. Normalization improves:

A. Storage
B. Data integrity
C. Redundancy
D. None
✔ Ans: B

40. When decomposition is NOT possible while preserving dependency + lossless join:

A. 2NF
B. 3NF
C. BCNF
D. 1NF
✔ Ans: C

Normal Forms

1. 1NF (First Normal Form)

Rule:

Example (Not in 1NF ❌):

Fixed Table (In 1NF ✅):

✅ Super Simple Definition:

2. 2NF (Second Normal Form)

Step 1: Recall 1NF (First Normal Form)

Step 2: What is 2NF?

Step 3: Example (Not in 2NF)

Step 4: Fix it → Convert to 2NF

✅ Super Simple Definition:

3. 3NF (Third Normal Form)

Step 1: Recall 2NF

Step 2: What is 3NF?

Step 3: Example (Not in 3NF)

Step 4: Fix it → Convert to 3NF

✅ Super Simple Definition:

4. BCNF (Boyce-Codd Normal Form)

Step 1: Recall 3NF

Step 2: What is BCNF?

Step 3: Example (Not in BCNF)

Step 4: Fix it → Convert to BCNF

✅ Super Simple Definition:

Key Differences:

Quick Tips to Remember:

✅ MCQs on NORMAL FORMS

1. Which of the following is required for a relation to be in 1NF?

2. A table violates 1NF when it contains:

3. A relation is in 2NF if it is in 1NF and:

4. Partial dependency occurs when:

5. A relation is in 3NF if it is in 2NF and:

6. Transitive dependency means:

7. A table in BCNF must be in:

8. Which normal form eliminates all functional dependency anomalies?

9. The highest normal form based on functional dependencies only is:

10. A multi-valued dependency exists when:

11. A relation is in 4NF if it is in BCNF and:

12. 5NF deals with

13. The process of converting an ER model to tables is called:

14. Normalization is used to:

15. Update anomalies occur due to:

16. Which anomaly is removed by 1NF?

17. Which normal form removes partial dependencies?

18. Which normal form ensures no transitive dependency?

19. BCNF is stronger than 3NF because:

20. A table is in BCNF but not in 4NF when:

21. Normalization helps in:

22. The condition for 3NF is:

23. Functional dependencies are used in determining:

24. If a relation has only single candidate key, BCNF and 3NF:

25. Which of the following is NOT true about normalization?

26. The decomposition is lossless when:

27. Dependency preservation means:

28. Which normal form is based on multivalued dependency?

29. Which normal form is based on join dependency?

30. A table is considered normalized when it is at least:

🚀 TOP 40 MOST IMPORTANT MCQs ON NORMAL FORMS

1. Which of the following is removed by 1NF?

2. 2NF removes which type of dependency?

3. A table is in 3NF if:

4. BCNF is stricter than 3NF because:

5. A transitive dependency exists when:

6. Which normal form deals with multi-valued dependency?

7. Join dependency is handled in:

8. A decomposition is lossless if:

9. 3NF allows which dependency that BCNF does NOT?

10. Which best describes normalization?

11. Update anomalies are caused due to:

12. A relation is in BCNF if:

13. Which normal form is based on only functional dependencies?

14. Partial dependency occurs when:

15. Transitive dependency is allowed in:

16. Most real-world databases use which normal form?

17. Functional dependencies help in:

18. Which NF eliminates transitive dependencies?

19. A relation with multi-valued dependency but no functional dependency violation belongs to:

20. Which normal form ensures no redundancy due to multiple independent attributes?

21. In 3NF, a non-prime attribute:

22. A table has attributes A, B, C. If A → B and B → C, then A → C is:

**9. The highest normal form based on functional dependencies only is:**

**18. Which NF eliminates transitive dependencies?**