Select only the fields a user needs
Choose the smallest useful set of columns for a report or screen.
Section 9 · Databases
Exam scope and assessment notes
This sequence follows Cambridge IGCSE Computer Science 0478, 2026–2028 syllabus Version 6, Topic 9. It covers single-table databases only and the specified SELECT, FROM, WHERE, ORDER BY, SUM, COUNT, AND and OR content. The official specimen also demonstrates NOT in a filter. Multi-table joins, GROUP BY, database implementation and the separate 2029–2031 syllabus are not mapped here. Practice is original, self-checked and does not award an official Cambridge grade. Full timed papers and human subject-teacher review remain outstanding.
Before you begin
- Be able to read a small table and compare values. Each lesson introduces the database and SQL terms it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
If a report asks only for names, which field should SELECT return?
What you will learn
- Map a question to returned fields
- Use comma-separated field names
- Explain why a query may omit other columns
The field list answers the request
Translate a request such as ‘show each title and date’ into the fields needed after SELECT. Do not include unrelated fields unless the output requires them.
Separate multiple field names with commas, then specify the table after FROM.
Projection changes the result shape
The result contains only the selected columns, even though the source table may have more fields.
A result can still contain repeated rows or field values if the source records repeat. SELECT does not automatically remove duplicates in this syllabus content.
Pause and explain
A table has ID, Name, Date and Paid. A report needs Name and Date. Which list follows SELECT?
Worked example
A report needs a show title and whether it is sold out. A table PERFORMANCES contains ShowID, Title, Date and SoldOut. Write the query.
Show the worked solution
- Identify the requested Title and SoldOut fields.
- Use PERFORMANCES as the source.
- Do not include other fields.
Answer SELECT Title, SoldOut FROM PERFORMANCES;
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Write a query to return a learner's Name and YearGroup from LEARNERS.
Give me a hint
Use the exact two fields requested.
Compare my reasoning
- Put Name and YearGroup after SELECT.
- Put LEARNERS after FROM.
- End the query.
SELECT Name, YearGroup FROM LEARNERS;
Look for these in your work
- Correct field list
- Correct table
A stored table has 8 fields but a notice needs only EventName and EventDate. Why is it reasonable to return just those two?
Give me a hint
Match output to the user task.
Compare my reasoning
- The notice requires only name and date.
- Other fields add no needed information.
- A smaller result is easier to interpret.
Select only EventName and EventDate because they satisfy the notice's requirement.
Look for these in your work
- Need identified
- Relevant fields
A query returns CustomerName, Address, PasswordHint and OrderTotal for a delivery label. Which fields should remain and why?
Give me a hint
A delivery label needs identity and location.
Compare my reasoning
- Keep CustomerName and Address.
- OrderTotal is not needed on the label.
- PasswordHint is unrelated and sensitive, so omit it.
Return CustomerName and Address only; the other fields do not belong on a delivery label.
Look for these in your work
- Relevant fields
- Unneeded fields removed
Common mistakes
- Returning every field when the request needs only two
- Leaving a comma between the final field and FROM
- Assuming SELECT removes duplicate values
What can you explain now?
What determines the fields placed after SELECT?
Compare with the explanation
The information the query must return
Choose columns that answer the request.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How do you decide which fields belong after SELECT?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.