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Practise 39 exam-style questions on SQL queries for Cambridge IGCSE Computer Science (Paper 2). Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
The table shows the database table Bookings for a hotel.
Give the output from this SQL query:
SELECT SUM(Cost)
FROM Bookings
WHERE RoomType = 'Double';
1025.00
Three bookings are for a Double room: 285.00 + 170.00 + 570.00 = 1025.00. SUM returns one total, not a list of values.
1025 (1025.00)
The table shows the database table Weather.
Give the output from each of these two SQL queries.
Query 1:
SELECT SUM(Rainfall)
FROM Weather
WHERE Town = 'Cardiff';Query 2:
SELECT COUNT(RecordID)
FROM Weather
WHERE Rainfall = 0.0;
Query 1: 4.9
Query 2: 3
Query 1 adds Cardiff's rainfall values: 3.1 + 0.6 + 1.2 = 4.9. Query 2 counts the records with no rain, W2, W5 and W7, giving 3.
Query 1: 4.9
Query 2: 3
The table shows the database table Orders for a café.
Write an SQL query to output the total quantity of Latte that has been ordered.
SELECT SUM(Quantity)
FROM Orders
WHERE Item = 'Latte';The total quantity is found by adding the Quantity values, which needs SUM. COUNT would only give the number of Latte orders (2), not the number of lattes ordered (3).
SELECT SUM(Quantity)
Do not accept COUNT.
FROM Orders
WHERE Item = 'Latte'
The table shows the database table Students, which stores each student's test marks.
A teacher wants a query that gives exactly this output:
Cerys 91
Femi 82
Hugo 74
Dev 70
Write an SQL query that would produce this output.
SELECT Name, English
FROM Students
WHERE English >= 70
ORDER BY English DESC;The numbers in the output match the English marks, so the fields are Name and English. The four students are the only ones with 70 or more in English, and the marks go from highest to lowest, so the sort is descending on English.
SELECT Name, English
Both fields in this order, no others.
FROM Students
A WHERE condition that selects exactly these four students, e.g. WHERE English >= 70
Accept any condition giving exactly these records, e.g. English > 65 or English >= 66. Do not accept English > 70 (excludes Dev).
ORDER BY English DESC
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