What do you understand by terms ‘primary key’ and ‘secondary key’ in a database?

What do you understand by terms ‘primary key’ and ‘secondary key’ in
a database?

Answer.
A primary key is a field that identifies each record in a database table
admitting that the primary key must contain its UNIQUE values.
A secondary key shows the secondary value that is unique for each
record. It can be used to identify the record and it is usually indexed.
It is also termed as Alternate key.