Database Concepts notes · Kaya Mo ’To

Database Concepts

Expect relational concepts (keys, relationships, normalization), SQL reading and writing, and transaction properties. The 2023 DICT FAQ lists database manipulation among the hands-on areas, so practise writing SQL by hand.

2023 FAQ (copy)Scope: Relational model, keys, normalization, SQL, transactions.

§1 Keys and relationships

§2 Normal forms

Form	Requirement
1NF	Atomic values; no repeating groups
2NF	1NF + no partial dependency on part of a composite key
3NF	2NF + no transitive dependency (non-key → non-key)

§3 SQL you should be able to write

Task	Statement
Create	CREATE TABLE item (id INT PRIMARY KEY, name VARCHAR(80), qty INT);
Insert	INSERT INTO item (id, name, qty) VALUES (1, 'Bond paper', 20);
Read	SELECT name, qty FROM item WHERE qty < 10 ORDER BY name;
Update	UPDATE item SET qty = qty - 1 WHERE id = 1;
Delete	DELETE FROM item WHERE id = 1;
Aggregate	SELECT category, COUNT(*) FROM item GROUP BY category;

§4 ACID

! Common traps

Writing UPDATE or DELETE without WHERE.
Using WHERE to filter aggregates — use HAVING.

Coverage source: 2023 ICT Proficiency Certification Examination FAQs (file dated 14 Feb 2023) (third-party copy)