Question Three
Answer
Super key is a set of one or more attributes that, taken collectively, allow us to identify uniquely a tuple in the relation
Candidate key is any set of one or more columns whose combined values are unique among all occurrences Since a null value is not guaranteed to be unique, no component of a candidate key is allowed to be null. There can be any number of candidate keys in a table
Primary key of any table is any candidate key of that table which the database designer arbitrarily designates as "primary". The primary key may be selected for convenience, comprehension, performance, or any other reasons
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