Define the database concepts: primary key, candidate key and superkey. Is a superkey always a key? Explain.
What will be an ideal response?
Each relation must have a primary key, which is an attribute orset of attributes used to uniquely
identify tuples in the relation. Thus any legal instance of a relation R cannot contain distinct
tuples which agree on the value of the primary key but not on the remaining set of attributes.
Every tuple in a relation has a unique value for the primary key.
Superkey is any set of attributes which satisfies the uniqueness condition
Primary key (or candidate key) a minimal superkey; that is, no proper subset of the key is a
superkey. primary key one key must be designated as the primary key.
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An unordered list is easily read by assistive technologies, so it meets accessibility requirements.
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