eli5 What is a Candidate Key? [Normalisation Process]

Question

I know it’s a basic question but I can find a simple answer.

Is it just multiple primary keys?

In: 19

Answer 1

It is a key which is eligible to be a primary key, it is also unique. There maybe multiple candidate keys in a table out of that we select one as the primary key, which is the most suitable for a particular table. For an example in Employee table there is employeeId and passportNo, both are unique so they are eligible to be primary key so they are called the candidate key. But out of that employeeId is the most preferred to become the primary key since it is the Employee table.