While SELECT queries retrieve data, real database systems must also be able to change data. In IB Computer Science, this is done using three core SQL commands: INSERT, UPDATE, and DELETE. These commands allow databases to stay accurate, current, and useful.
IB examiners expect students to understand what each command does, when it should be used, and the risks involved if used incorrectly.
Why Data Modification Matters
Databases are not static. They must:
- Add new records
- Correct existing data
- Remove outdated or incorrect records
INSERT, UPDATE, and DELETE allow databases to reflect real-world changes, such as:
- New students enrolling
- Address changes
- Old records being removed
Understanding these commands is essential for explaining how databases are maintained.
What Is INSERT?
The INSERT command is used to add new records to a table.
INSERT:
- Creates a new row
- Adds data to specified fields
- Does not affect existing records
INSERT is used when:
- New data needs to be stored
- A new entity is added to the system
In IB terms, INSERT supports data creation.
Why INSERT Must Be Used Carefully
When inserting data:
- Field order must match values
- Data types must be correct
- Primary key values must be unique
If incorrect data is inserted:
- Errors may occur
- Data integrity may be compromised
IB students should recognise that databases enforce rules to prevent invalid inserts.
What Is UPDATE?
The UPDATE command is used to modify existing records.
UPDATE:
- Changes values in one or more fields
- Applies only to records that meet conditions
UPDATE is commonly used to:
- Correct errors
- Change contact details
- Update statuses
In IB Computer Science, UPDATE is linked to data maintenance.
The Importance of WHERE with UPDATE
UPDATE commands are usually combined with a WHERE clause.
Without WHERE:
- Every record in the table may be updated
This is a common IB exam warning point.
Strong answers explain that:
- WHERE ensures only intended records are changed
- Missing WHERE can cause serious data loss
What Is DELETE?
The DELETE command is used to remove records from a table.
DELETE:
- Permanently removes rows
- Cannot be easily undone
DELETE is used when:
- Records are no longer needed
- Data must be removed for accuracy or compliance
In IB exams, DELETE is often associated with risk and caution.
DELETE and WHERE: A Critical Link
Like UPDATE, DELETE should almost always use a WHERE clause.
Without WHERE:
- All records in the table are deleted
IB students should highlight this risk clearly in explanations.
Comparing INSERT, UPDATE, and DELETE
Strong IB answers compare their purposes:
- INSERT: adds new records
- UPDATE: modifies existing records
- DELETE: removes records
Together, these commands support full data management.
Common Student Mistakes
Students often:
- Forget that DELETE is permanent
- Ignore the role of WHERE
- Confuse UPDATE with INSERT
- Describe effects vaguely
Precision is essential.
How These Commands Appear in IB Exams
IB questions may ask students to:
- Choose the correct command for a task
- Explain what a command does
- Identify risks in a query
- Modify a query safely
Clear cause-and-effect explanations score highest.
Final Thoughts
INSERT, UPDATE, and DELETE allow databases to stay accurate and relevant by adding, changing, and removing data. While powerful, these commands must be used carefully to protect data integrity.
Understanding how and why these commands are used allows IB Computer Science students to explain real-world database maintenance clearly and confidently — exactly what examiners expect.
