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1.3 Exchanging data

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 shrink data, keep it secret, and verify it without storing the original?

Compression (lossy and lossless, run length encoding and dictionary coding), encryption (symmetric and asymmetric) and hashing, including their characteristics, differences and appropriate uses.
An OCR H446 answer on compression, encryption and hashing: lossy versus lossless compression with run length encoding and dictionary coding, symmetric versus asymmetric encryption, and how hashing works, with the characteristics, differences and appropriate uses of each.
13 min answer →

How does a relational database organise data into tables, and what does normalising to third normal form achieve?

The relational database model: entities, attributes, primary and foreign keys, entity relationships, the difference between a flat file and a relational database, and normalisation to first, second and third normal form.
An OCR H446 answer on relational databases and normalisation: entities, attributes, primary and foreign keys, entity relationships, the difference between flat-file and relational databases, and how to normalise data to first, second and third normal form.
14 min answer →

How do we create, query and modify the data in a relational database using SQL?

Structured Query Language (SQL): defining tables, and using SELECT, FROM, WHERE, ORDER BY, INSERT INTO, UPDATE, DELETE and joining tables to query and maintain a relational database, with referential integrity.
An OCR H446 answer on Structured Query Language: defining tables and using SELECT, FROM, WHERE, ORDER BY, INSERT INTO, UPDATE and DELETE, joining tables across a relationship, and the role of referential integrity in a relational database.
13 min answer →

How does a database stay correct when many users change it at once?

Transaction processing and the ACID properties (atomicity, consistency, isolation, durability), record locking and serialisation to manage concurrent access, and redundancy through commitment ordering and backups.
An OCR H446 answer on transaction processing and managing concurrent access: the ACID properties (atomicity, consistency, isolation, durability), record locking and serialisation to prevent conflicting updates, and redundancy through commitment ordering and backups.
13 min answer →