ITPEC FE Subject A October 2025 Question 18
ITPEC FE Subject A October 2025 — Question 18 of 60
Attributes in the Relational Model — attribute order has no significance in a relation.
In the relational model, a relation is defined as a set of attributes (not an ordered list), so reordering columns does not change the relation.
Core rules for attributes:
- Every attribute must have a name (unnamed attributes are not allowed)
- Attribute names within a relation must be unique
- Domains of different attributes can overlap (e.g., two columns can both be VARCHAR)
- The order of attributes is irrelevant — rearranging columns produces the same relation
Why not others:
- (a) Attributes must always have a name — it is part of the relation schema definition
- (b) Domains can overlap — e.g., first_name and last_name can share the same domain
- (c) Attribute names must be unique within a single relation
Key rule: A relation is a set of tuples over named attributes — order of attributes and order of tuples are both meaningless.
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