IB Computer Science HL · Year 2 · Lesson 45

Normalization to 3NF and denormalization

Database design moves from real-world entities to schemas, keys, relationships and normalized tables.

Paper 150 minutesA3.2.5 · A3.2.6 · A3.2.7
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Today’s targets

What you need to be able to do

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  • ExplainThe difference between normal forms
  • ConstructA database normalized to 3NF for a range of real-world scenarios
  • EvaluateThe need for denormalizing databases
A3.2.5A3.2.6A3.2.7
Paper 1 lensMatch the depth of every response to the command term. Previously learned content can move quickly, but retrieval must still be accurate.
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Retrieve

Rapid Recall Deck

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Say the answer aloud before flipping. Mark secure knowledge quickly and spend time on the gaps.

  • What is required for first normal form (1NF)?: Values are atomic rather than repeating/multi-valued groups, and records can be uniquely identified.
  • What problem does second normal form (2NF) remove?: Partial-key dependencies: a non-key attribute must not depend on only part of a composite key.
  • What problem does third normal form (3NF) remove?: Transitive/non-key dependencies: non-key attributes should depend on the key, not on other non-key attributes.
  • What is a functional dependency?: A relationship where the value of one attribute or set of attributes determines another attribute's value.
  • Why normalize a relational database?: To reduce redundancy and update/insert/delete anomalies while improving consistency and integrity.
  • Why might a database be deliberately denormalized?: In read-intensive systems it can simplify queries and improve performance, but it increases redundancy and the risk of inconsistency.
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A3.2.5 + A3.2.6 · Learn

Core knowledge and application

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A3.2.5Explain

The difference between normal forms

Database design moves from real-world entities to schemas, keys, relationships and normalized tables.

Exam moveGive the mechanism or relationship and make the reasons/causes explicit.
Required detail 1First normal form (1NF), second normal form (2NF), third normal form (3NF)
Required detail 2The terms atomicity, unique identification, functional dependencies, partial-key dependencies, non- key/transitive dependencies
Required detail 3Normalization issues can encompass data duplication, missing data, and a range of dependency concerns, including data dependencies, composite key dependencies, transitive dependencies, and multi-valued dependencies
Assessment boundaryExternal assessment goes to a maximum of 3NF; multi-valued dependencies/4NF/BCNF are not assessed.

Explain it without notes

Explain: The difference between normal forms in the context of a library database being redesigned to reduce redundancy and anomalies.

  • First normal form (1NF), second normal form (2NF), third normal form (3NF)
  • The terms atomicity, unique identification, functional dependencies, partial-key dependencies, non- key/transitive dependencies
  • Normalization issues can encompass data duplication, missing data, and a range of dependency concerns, including data dependencies, composite key dependencies, transitive dependencies, and multi-valued dependencies
A3.2.6Construct

A database normalized to 3NF for a range of real-world scenarios

Database design moves from real-world entities to schemas, keys, relationships and normalized tables.

Exam moveProduce the required code, diagram, query, model or representation accurately.
Required detail 1Examples may include library management, hospital management, e-commerce platforms, school management, employee management, inventory management, police crime reporting
Assessment boundaryExternal assessment goes to a maximum of 3NF; multi-valued dependencies/4NF/BCNF are not assessed.

Explain it without notes

Construct: A database normalized to 3NF for a range of real-world scenarios in the context of a library database being redesigned to reduce redundancy and anomalies.

  • Examples may include library management, hospital management, e-commerce platforms, school management, employee management, inventory management, police crime reporting
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A3.2.7 · Learn

Core knowledge and application

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A3.2.7Evaluate

The need for denormalizing databases

Database design moves from real-world entities to schemas, keys, relationships and normalized tables.

Exam moveWeigh strengths and limitations in context, then reach a supported judgement.
Required detail 1The advantages and disadvantages of normalizing and denormalizing databases
Required detail 2Situations where denormalization can enhance performance, particularly in read-intensive applications
Required detail 3The balance between straightforward query structures and the risk of data redundancy in denormalized schemas

Explain it without notes

Evaluate: The need for denormalizing databases in the context of a library database being redesigned to reduce redundancy and anomalies.

  • The advantages and disadvantages of normalizing and denormalizing databases
  • Situations where denormalization can enhance performance, particularly in read-intensive applications
  • The balance between straightforward query structures and the risk of data redundancy in denormalized schemas
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Worked example · A3.2.5–A3.2.7

Normalize a database to 3NF

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Start with:

ENROLLMENT(StudentID, StudentName, CourseID, CourseName, TeacherID, TeacherName, Grade)

Composite key: (StudentID, CourseID).

1NFEnsure every field is atomic and rows are uniquely identifiable. Repeating groups are removed.
2NFRemove partial-key dependencies: StudentName depends only on StudentID; course information depends only on CourseID.
3NFRemove transitive/non-key dependencies: TeacherName depends on TeacherID, not directly on the course key.
STUDENT(StudentID PK, StudentName)
TEACHER(TeacherID PK, TeacherName)
COURSE(CourseID PK, CourseName, TeacherID FK)
ENROLLMENT(StudentID PK/FK, CourseID PK/FK, Grade)
External-assessment boundaryBe ready to construct through 3NF. Higher normal forms such as BCNF/4NF are not required. Denormalization may improve read performance, but it reintroduces redundancy and update-consistency risks.
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Apply

Transfer to a new scenario

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ScenarioA library database being redesigned to reduce redundancy and anomalies needs a design or technical decision related to today’s topic. Explain what matters and why.
  • First normal form (1NF), second normal form (2NF), third normal form (3NF)
  • The terms atomicity, unique identification, functional dependencies, partial-key dependencies, non- key/transitive dependencies
  • Examples may include library management, hospital management, e-commerce platforms, school management, employee management, inventory management, police crime reporting
  • The advantages and disadvantages of normalizing and denormalizing databases
  • Situations where denormalization can enhance performance, particularly in read-intensive applications
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Exam lens

Paper 1 practice

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Build the response before checking notesUse precise terminology and match the required depth.
  1. Explain: The difference between normal forms in the context of a library database being redesigned to reduce redundancy and anomalies.
  2. Construct: A database normalized to 3NF for a range of real-world scenarios in the context of a library database being redesigned to reduce redundancy and anomalies.
  3. Evaluate: The need for denormalizing databases in the context of a library database being redesigned to reduce redundancy and anomalies.
Self-checkAnswer the exact command term. For explain, include mechanism/reason; for compare, pair criteria; for discuss/evaluate/justify, build supported reasoning and a conclusion.
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Homework

Finish the learning cycle

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IA — main task

Complete Criterion E and final IA quality checks. Evaluate the product against success criteria and propose specific, feasible improvements.

Syllabus — short

Complete a short Paper 1 retrieval task; keep the IA as the main workload.

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End of Lesson 45.