(a) Explain the following database management terms; (i) entities (ii) attributes (iii) relationships (b)(i) Define cardinality in database management. (ii)...

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This question tests core database-modelling terms and cardinality.

(a) Database-management terms.

• (i) Entity: a real-world object, person, place, event or concept about which data is stored in a database (for example a Student, a Book or a Customer). Each entity becomes a table.
• (ii) Attribute: a property or characteristic that describes an entity (for example a Student's name, registration number or date of birth). Attributes form the columns/fields of the table.
• (iii) Relationship: a meaningful association or link between two or more entities (for example a Student "borrows" a Book), showing how their records are connected.

(b)(i) Cardinality. Cardinality describes the number of instances of one entity that can be associated with instances of another entity in a relationship, that is the degree of the relationship between two tables.

(b)(ii) Three cardinality relationships.

• One-to-one (1:1): one record in the first entity relates to exactly one record in the second.
• One-to-many (1:M): one record in the first entity relates to many records in the second.
• Many-to-many (M:N): many records in the first entity relate to many records in the second.

Examination reminder: keep the three terms in order - an entity is the thing, an attribute describes it, and a relationship links entities; cardinality then counts how many on each side (1:1, 1:M, M:N).