O Level Computer Science: Databases (Cambridge 2210)

Topic 9 of Cambridge O Level Computer Science (2210) covers single-table databases: setting one up from a description of the data, choosing data types and validation for its fields, choosing a primary key, and using structured query language (SQL) to get information out of it. The SQL is limited to a short list of keywords, so this is a topic where careful practice quickly turns into reliable marks on Paper 2.

Where Topic 9 sits in 2210

Topic 9 is part of “Algorithms, programming and logic” and is assessed on Paper 2 (1 hour 45 minutes, 75 marks). Its content matches Topic 9 of Cambridge IGCSE Computer Science (0478). There are no numbered sub-topics: the syllabus lists four learning outcomes — define a single-table database, suggest data types, understand and identify a primary key, and read, understand and complete SQL scripts.

What a database table is made of

A database is an organised store of data that can be searched, sorted and updated. In 2210 every database is a single table.

• A field is one category of data stored for every item — a column, such as DailyRate.
• A record is all the data about one item — a row, such as one car.
• A primary key is a field whose value is unique for every record, so each record can be identified without confusion.

Here is the table used in this guide. It belongs to a car-hire company and is called Car.

CarReg	Make	Seats	DailyRate	Electric	LastService
LEA 2041	Suzuki	5	35.00	FALSE	12/03/2026
KHI 7712	Toyota	7	55.50	FALSE	02/05/2026
ISB 3390	Hyundai	5	48.00	TRUE	20/01/2026
LEA 5218	Toyota	5	42.25	TRUE	15/04/2026
MUX 6603	Honda	4	30.00	FALSE	28/02/2026

It has 6 fields and 5 records. CarReg is the primary key: every registration is different, whereas makes, seat counts and rates repeat.

Defining a table from a description

When a question describes the data an organisation wants to keep, work through the description and for each item decide:

1. a field name — short and meaningful, without spaces (DailyRate, not the price per day);
2. a data type from the syllabus list;
3. any sensible validation — the syllabus links validation directly to defining the table.

Data types

Data type	Use	Field in the Car table
Text/alphanumeric	Letters and numbers, or digits not used in calculations	CarReg, Make
Character	A single character	(e.g. a fuel code ‘P’ or ‘D’)
Boolean	Two possible values	Electric
Integer	Whole numbers	Seats
Real	Numbers with a fractional part	DailyRate
Date/time	Dates and times	LastService

Validation for the fields

Field	Suitable check
CarReg	Presence check; format check (three letters, a space, four digits)
Seats	Range check, e.g. 2 to 9
DailyRate	Range check, greater than 0; type check (real)
LastService	Type check that it is a valid date

Choosing a primary key

A good primary key is unique, always present and unlikely to change. If no natural field is unique — for example a table of club members where two people could share a name and birthday — create one, such as MemberID. Exam questions often ask you to explain why a particular field would not work: always point out that its values can be repeated.

SQL in 2210

The syllabus limits SQL to these keywords: SELECT, FROM, WHERE, ORDER BY ... ASC, ORDER BY ... DESC, SUM, COUNT, AND, OR. You must be able to read and complete scripts, and identify the output a statement gives for the data in a table.

The standard shape:

SELECT CarReg, DailyRate
FROM Car
WHERE Seats = 5
ORDER BY DailyRate DESC;

• After SELECT, list only the fields requested, separated by commas (* means every field).
• After FROM, give the table name.
• WHERE filters the records; text values go in single quotes (Make = 'Toyota'), numbers and Boolean values do not.
• ORDER BY sorts the results: ASC for smallest/A first, DESC for largest/Z first.
• SUM(field) adds a numeric field over the selected records; COUNT(*) counts the selected records.

Worked example 1: writing a query

List the registration and make of every electric car, in alphabetical order of make.

SELECT CarReg, Make
FROM Car
WHERE Electric = TRUE
ORDER BY Make ASC;

Output: ISB 3390 Hyundai; LEA 5218 Toyota.

Worked example 2: two conditions

Count the cars with five seats that cost less than 45.00 per day.

SELECT COUNT(*)
FROM Car
WHERE Seats = 5 AND DailyRate < 45.00;

Records LEA 2041 (35.00) and LEA 5218 (42.25) meet both conditions; ISB 3390 has five seats but costs 48.00. Output: 2.

Worked example 3: identifying the output with OR

SELECT Make, Seats
FROM Car
WHERE Make = 'Honda' OR Seats > 5
ORDER BY Seats ASC;

Honda gives MUX 6603 (4 seats); more than 5 seats gives KHI 7712 (7 seats). Sorted by seats ascending, the output is: Honda 4; Toyota 7.

Worked example 4: SUM

SELECT SUM(DailyRate) FROM Car WHERE Make = 'Toyota'; returns 55.50 + 42.25 = 97.75 — the cost of hiring both Toyotas for one day.

How to approach it

Learn the four-line SQL shape until you can write it without thinking, then practise “identify the output” questions by first ticking the records that match WHERE, then keeping only the SELECT fields, then applying ORDER BY. In design questions, give a data type for every field and justify the primary key with the word “unique”.

Frequently asked questions

Does 2210 include databases with more than one table? No. Topic 9 is limited to single-table databases, and all SQL queries work on one table.

Should a car registration be text or integer? Text/alphanumeric. It contains letters and spaces, and it is never used in calculations.

What is the difference between SUM and COUNT? SUM adds up the values in a numeric field for the records selected; COUNT counts how many records are selected.

Can I use SQL commands such as INSERT or UPDATE? They are not in the 2210 syllabus. Questions only ask you to query data with the listed keywords.

Official syllabus

Cambridge International, Cambridge O Level Computer Science (2210) syllabus for examination in 2026, 2027 and 2028: official syllabus PDF, Subject content, section 9 “Databases”. Checked 2026-11-08.

Next steps: revise from the Databases revision notes, then practise with the Databases practice questions.