ITPEC IP October 2020 Question 26
ITPEC IP October 2020 — Question 26 of 100
A primary key is specified so that every record in a relational table can be uniquely identified. Its value, or combination of values for a composite key, must distinguish one row from all others and cannot be null.
Answer (d)
Why not others:
- a key does not indicate whether arithmetic is permitted
- ordinary columns can also be searched, so searchability is not the defining purpose
- other tables may intentionally reference a primary key through foreign keys
Key rule: Primary keys enforce entity identity; foreign keys use matching values to represent relationships between tables.
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