keys
primary key
A primary key is the primary identifier for a table. And is attached to one or more columns whose combined values uniquely identify every row in the table. Every table must have a primary key.
foreign key
A primary key of one table that appears as an attribute in another table and acts to provide a logical relationship between the two tables.
alternative key
An alternate key is a key associated with one or more columns whose values uniquely identify every row in the table, but which is not the primary key.
candidate key
An attribute, or combination of attributes, that uniquely identifies a row in a relation.
super key
Any combination of field within a table that uniquely identifies each record within the table.