What does the databases topic cover?

It covers conceptual data modelling with entities, attributes and relationships and ER diagrams, relational databases with primary and foreign keys, the problems of data redundancy, normalisation to first, second and third normal form, SQL for retrieving and modifying data including joins, and transaction processing with the ACID properties, record locking, deadlock and recovery.

What is the difference between a primary key and a foreign key?

A primary key is an attribute (or combination) that uniquely identifies each record within its own table. A foreign key is an attribute in one table that is the primary key of another table, used to create a link or relationship between the two tables. Together they let a relational database hold related data across linked tables without repetition.

What is third normal form?

A table is in third normal form when it is in second normal form and has no transitive dependencies, meaning no non-key attribute depends on another non-key attribute. The summary is that every non-key attribute depends on the key, the whole key, and nothing but the key. Normalisation to 3NF removes redundancy and the update, insertion and deletion anomalies.

Why must UPDATE and DELETE statements include a WHERE clause?

The WHERE clause selects which records the statement applies to. Without it, an UPDATE changes every record in the table and a DELETE removes every record, which is almost never what is intended. Always include a WHERE clause to target only the specific records you mean to change or remove.

What are the ACID properties?

ACID guarantees reliable transactions. Atomicity means a transaction is all or nothing. Consistency means it takes the database from one valid state to another. Isolation means concurrent transactions do not interfere with each other. Durability means once a transaction is committed its changes are permanent and survive a crash. Record locking and a transaction log help enforce these.

EnglandComputer Science

AQA A-Level Computer Science 4.10 Fundamentals of databases: data modelling, normalisation, SQL and transactions

A deep-dive AQA A-Level Computer Science guide to 4.10 Fundamentals of databases. Covers conceptual data modelling and ER diagrams, relational databases with primary and foreign keys, normalisation to third normal form, SQL queries and data modification, and transaction processing with the ACID properties.

Generated by Claude Opus 4.817 min read4.10Updated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

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What the databases topic actually demands
Conceptual data modelling
Relational databases and normalisation
SQL
Transaction processing
Check your knowledge

What the databases topic actually demands

Databases are how large systems store structured data reliably. AQA expects you to model data, normalise to remove redundancy, write SQL to query and change data, and explain how transactions keep data consistent under concurrent access.

Conceptual data modelling

Identify the entities a system stores data about, their attributes, and the relationships between them, and draw an ER diagram labelled with the degree (one-to-one, one-to-many, many-to-many). A many-to-many relationship is resolved with a linking (junction) table, creating two one-to-many relationships.

Relational databases and normalisation

A relational database links tables by primary and foreign keys. Poor structure causes redundancy and update, insertion and deletion anomalies. Normalisation fixes this: 1NF removes repeating groups, 2NF removes partial dependencies, and 3NF removes transitive dependencies so every non-key attribute depends only on the primary key.

SQL

Retrieve data with SELECT ... FROM ... WHERE ... ORDER BY, combine tables with a join matching a foreign key to a primary key, and modify data with INSERT INTO, UPDATE ... SET and DELETE FROM, always using a WHERE clause to target the right records.

Transaction processing

A transaction is a single logical unit of work that must be all or nothing. The ACID properties (atomicity, consistency, isolation, durability) guarantee reliability. Record locking prevents lost updates but can cause deadlock, and redundancy and a transaction log allow recovery to a consistent state after a failure.

Check your knowledge

State the difference between an entity and an attribute. (2 marks)
Explain how a many-to-many relationship is resolved. (2 marks)
State the purpose of a foreign key. (2 marks)
State the condition a table must meet to be in third normal form. (2 marks)
Write SQL to list the names of students with a mark above 60, highest first. (2 marks)
State why a WHERE clause is essential in a DELETE statement. (1 mark)
State what atomicity means in the ACID properties. (1 mark)
Explain how a deadlock can arise from record locking. (2 marks)

Sources & how we know this

AQA A-level Computer Science (7517) specification — AQA (2015)