WA Computer Science ATAR Unit 2 Definitions Worksheet: Data Management and Cyber Security (Modules 28–122)
Name:
Date:
Class:
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Key terms
Write what each term means, in your own words.
1
PRIMARY KEY (studentId, subjectId)
2
data anomaly
3
functional dependency
4
1NF
5
2NF
6
3NF
7
Normalise to 3NF
8
IS NULL
9
integrity
10
Availability
Answer Key
WA Computer Science ATAR Unit 2 · Modules 28–122 · Student wording will vary for definitions
1PRIMARY KEY (studentId, subjectId) — A composite primary key: two or more fields together identify each record uniquely. Each field can repeat alone, but the pair cannot. Used in junction tables.
2data anomaly — A problem caused by redundant data in one table: adding, changing or deleting a record leads to missing data, inconsistent copies or accidental loss of other facts.
3functional dependency — A field is functionally dependent on another when the other field's value determines it. The determinant fixes the value: studentId determines studentName.
41NF — A table is in 1NF when every field holds one atomic value, there are no repeating groups, and each record is identified by a key.
52NF — A table in 1NF where no non-key field depends on only part of a composite key. Remove any partial dependency by splitting those fields into a new table.
63NF — A table in 2NF where no non-key field depends on another non-key field. Every field depends on the key, the whole key and nothing but the key.
7Normalise to 3NF — Take a table through 1NF, 2NF, then 3NF by removing repeating groups, then partial dependencies, then transitive dependencies, giving each new table its own key.
8IS NULL — NULL marks a missing value. Test for it with IS NULL or IS NOT NULL, because = NULL never matches. NULL is not a blank or 0, and aggregates ignore it.
9integrity — Data stays accurate, complete and unaltered unless an authorised person changes it. Tampering breaks integrity by altering data without permission.
10Availability — Authorised users can reach data and systems when they need them. Attacks like DDoS and hardware failure reduce it.