Super key and Candidate key?

Explain to me the difference between super key and candidate key? 

Simple a candidate key is an attribute (or attribute combination) that uniquely identifies each row in that table, with one additional important property: as soon as you remove any attribute from this candidate key attribute combination, the property of unique identification is gone. In other words, a table cannot contain two rows with the same candidate key values at any time. For example, the attribute combination course code and start date is a candidate key for a table containing information about course offerings. If you remove the start date attribute, the remaining course code attribute is not a candidate key anymore: otherwise, you could offer courses only once. If you remove the course code attribute, the remaining start date attribute is not a candidate key anymore; otherwise, you would never be able to schedule two different courses to start on the same day.


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