In IB Computer Science, students often focus on SQL commands or definitions while overlooking a far more important idea: database design. A database can contain correct data and still be poorly designed, leading to errors, inefficiency, and security problems.
IB examiners expect students to understand why database design matters, what problems occur when design is weak, and how good design improves reliability and scalability.
What Is Database Design?
Database design is the process of:
- Planning how data will be stored
- Deciding how tables relate to each other
- Choosing appropriate keys
- Ensuring data accuracy and consistency
Good design happens before data is stored. Once a database is built poorly, fixing it later can be difficult and costly.
Problems Caused by Poor Database Design
Poorly designed databases often suffer from:
- Data duplication
- Inconsistent information
- Update errors
- Data loss
- Security weaknesses
For example:
- A customer address stored in multiple tables may not be updated everywhere
- Deleting a record may accidentally remove important information
- Incorrect relationships may allow invalid data to be entered
In IB exams, these issues are commonly referred to as anomalies.
Data Redundancy and Inconsistency
One of the biggest design problems is data redundancy.
When the same data is stored multiple times:
- Storage space is wasted
- Data may become inconsistent
- Errors become more likely
Good database design reduces redundancy by:
- Storing each data item once
- Linking tables using keys
This ensures that updates are safe and consistent.
The Role of Normalisation in Design
Normalisation is a key part of good database design.
By:
- Splitting data into related tables
- Removing unnecessary repetition
- Using primary and foreign keys
Normalisation ensures:
- Logical structure
- Accurate data
- Fewer update problems
IB students should understand that normalisation exists to support good design, not as a theoretical exercise.
Database Design and Data Integrity
Data integrity refers to the accuracy and reliability of data.
Good design protects data integrity by:
- Enforcing primary key uniqueness
- Ensuring foreign keys reference valid records
- Preventing invalid or inconsistent data
This is especially important in systems such as:
- Banking
- School records
- Medical databases
IB examiners often link database design directly to data integrity.
Security and Access Control
Database design also affects security.
Good design allows:
- Sensitive data to be separated
- Access rights to be controlled
- Users to see only what they need
Poor design can expose:
- Confidential information
- Critical system data
Design decisions directly influence how secure a system can be.
Scalability and Performance
Well-designed databases:
- Handle growth more easily
- Support multiple users
- Remain manageable as data increases
Poorly designed databases often become:
- Slow
- Difficult to modify
- Error-prone
IB students should recognise that good design supports long-term system success.
How This Appears in IB Exams
Students may be asked to:
- Explain why database design is important
- Identify design problems in a scenario
- Justify the use of normalisation
- Explain the impact of poor design
Clear explanations with cause-and-effect reasoning score highest.
Common Student Mistakes
Students often:
- Treat design as optional
- Focus only on SQL syntax
- Ignore long-term consequences
- Forget data integrity
IB exams reward understanding, not memorisation.
Final Thoughts
Database design determines how reliable, efficient, and secure a system will be. Good design reduces errors, protects data, and allows systems to grow safely over time.
Understanding why database design matters gives IB Computer Science students a strong foundation for databases, SQL, and real-world information systems — exactly what examiners expect.
