A primary key is a field that is used to uniquely identify a record in a table.
A secondary key is a field that can be used to access a table in a different way. It doesn’t have to uniquely identify a record but can be indexed for faster searching.
A foreign key is a field that links two tables together and has a many to one relationship. Foreign keys can be used to avoid data duplication.
This is an example of how Keys can be used:
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