Databases and SQL queries

Informatik GCSE Updated Wed 7 Oct 2026

A relational database stores data in tables that can be linked. SQL is the language used to search and change that data, and exam questions ask you to read and write short queries.

Part 1 of 3: Learn it

In short

A table holds records (rows); each record has fields (columns).
A primary key uniquely identifies each record; a foreign key links to another table.
SELECT fields FROM table WHERE condition ORDER BY field.

Where this is in your specification

Spec points: AQA 3.7.1 and 3.7.2, OCR 2.2.3, Edexcel 1.2.2 and 6.3.1

Board	Topic: Databases and SQL
AQA 8525	3.7.1 and 3.7.2
Edexcel 1CP2	1.2.2 and 6.3.1 (records), 6.4.2 (CSV text files)
OCR J277	2.2.3 (records, SQL, 2D arrays as tables, file handling)
Eduqas C500	5 Data organisation
Cambridge IGCSE 0478	9 Databases
National 5 C816 75	Database design and development

Tables, records and keys

A record is all the data about one item, such as one film. A field is one piece of data about it, such as its year. The primary key is a field whose value is different for every record, such as FilmID. A foreign key is a field in one table that is the primary key of another, which is how tables are linked without repeating data.

Reading data

SELECT Title, Year

FROM Films

WHERE Rating >= 4 AND Year > 2015

ORDER BY Year DESC

SELECT names the fields to show; * means every field.
FROM names the table.
WHERE filters records with a condition, using =, <, >, AND, OR. Text values go in quotes: Genre = 'Comedy'.
ORDER BY sorts the results: ASC for ascending (the default), DESC for descending.

Changing data

INSERT INTO Films (FilmID, Title, Year, Rating) VALUES (21, 'Tidewater', 2024, 4)
UPDATE Films SET Rating = 5 WHERE FilmID = 21
DELETE FROM Films WHERE Year < 1990

Without a WHERE clause, UPDATE and DELETE affect every record in the table.

Quick check

What does * mean in SELECT *?

Show the answer

Show every field.

Part 2 of 3: See it worked

Worked examples

Example 1

A table Pupils has fields PupilID, Surname, Form and Age. Write a query to show the surnames of every pupil in form 10B, in alphabetical order.

Field to show: Surname
Condition: Form = '10B'
Sort: ORDER BY Surname ASC

Answer: SELECT Surname FROM Pupils WHERE Form = '10B' ORDER BY Surname ASC

Example 2

Using the same table, write a query to show every field for pupils aged 15 or over.

Every field: SELECT *
Condition: Age >= 15

Answer: SELECT * FROM Pupils WHERE Age >= 15

Common mistakes

Leaving out FROM, or putting WHERE before FROM.
Forgetting quotes round text values in a condition.
Using a field that might repeat, such as Surname, as a primary key.
Running UPDATE or DELETE without a WHERE clause.

Quick check

What is a primary key?

Show the answer

A field whose value is unique for every record, so it identifies each one.

Part 3 of 3: Test yourself

Check yourself

Answer each one in your head or on paper first, then open it to check.

What does * mean in SELECT *?

Show every field.

What is a primary key?

A field whose value is unique for every record, so it identifies each one.

Which keyword sorts results from highest to lowest?

DESC, after ORDER BY and the field name.

Jobs that use this

Each link opens the job profile on the National Careers Service (England). In the rest of the UK: My World of Work (Scotland), Careers Wales, nidirect careers (Northern Ireland).

Diese Lernzettel sind auf Englisch, weil sie britischen Prüfungslehrplänen folgen.

Full lessons and marked practice for this course are coming soon to Brainlag Learn. See courses