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4.9 Fundamentals of databases

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do we model the data and relationships in a real-world system?

Understand conceptual data modelling, entities, attributes and relationships, entity relationship (ER) diagrams, and the degrees of relationship (one-to-one, one-to-many, many-to-many).
A focused answer to AQA A-Level Computer Science 4.10.1, covering conceptual data modelling, entities, attributes and relationships, entity relationship diagrams, and the degrees of relationship including resolving many-to-many.
8 min answer →

What is a relational database and why do we normalise to third normal form?

Understand relational databases, primary and foreign keys, the problems of data redundancy, and normalisation to first, second and third normal form.
A focused answer to AQA A-Level Computer Science 4.10.2, covering relational databases, primary and foreign keys, the problems of data redundancy, and normalisation to first, second and third normal form.
9 min answer →

How do we query and modify a relational database using SQL?

Understand SQL for retrieving data with SELECT, FROM, WHERE and ORDER BY, joining tables, and modifying data with INSERT, UPDATE and DELETE.
A focused answer to AQA A-Level Computer Science 4.10.3 and 4.10.4, covering SQL for retrieving data with SELECT, FROM, WHERE and ORDER BY, joining tables, and modifying data with INSERT, UPDATE and DELETE.
9 min answer →

How do databases keep data consistent and safe during concurrent transactions?

Understand transaction processing, the ACID properties, record locking and the deadlock that can result, redundancy and database recovery.
A focused answer to AQA A-Level Computer Science 4.10.5, covering transaction processing, the ACID properties, record locking and deadlock, redundancy, and database recovery from failure.
8 min answer →