ITPEC FE Morning April 2022 Question 24
ITPEC FE Morning April 2022 — Question 24 of 80
Attributes in the Relational Model — properties of columns in a relation.
Key rules of attributes in the relational model:
- •Every attribute must have a unique name within a relation
- •Domains can overlap — multiple attributes may share the same domain (e.g., both
INTEGER) - •Order of attributes does not matter — a relation is a set, not a sequence
- •Reordering columns produces the same relation
Why not others:
- (a) Every attribute must have a name — nameless attributes are not allowed
- (b) Domains of different attributes can overlap (e.g., two columns both using INTEGER)
- (c) Attribute names must be unique within a relation — duplicates are not permitted
Key rule: A relation is defined by its heading (set of named attributes) and body (set of tuples). Since it's a set, order is irrelevant.
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