Super Key
A set of one or more Attributes, which may include extra, unnecessary Attributes that together mean each Tuple in a Relation is unique. If you were to include all columns in a table this should be a Super Key as you should not have the same rows duplicated.
Example:
| UserId | UserName | Password | |
|---|---|---|---|
| 1 | AJones | alex.jones@abc.com | ######## |
| 2 | BSmith | bob.smith@def.com | ######## |
| 3 | CBloggs | chris.bloggs@xyz.com | ######## |
Possible Super Keys:
(UserId, UserName, Email, Password)
(UserId, UserName, Email)
(UserId, UserName, Password)
(UserId, Email, Password)
(UserId, UserName)
(UserId, Email)
(UserId, Password)
(UserId)
(UserName)
(Email)
(Password) cannot be used as you could have more than one user with the same password.