What is the difference between primary key and alternate key?

Answer 1

Primary key can be set to just one column whereas alternate key can be set to multiple columns. Refer Online tutorials for more!

Answer 2

Any key, which can act as a primary key,but isnt one is alternate key.

Answer 3

Primary key is the value in a coloumn of a table which can uniquely identify the entire row.Sometimes there can be more one coloumn in a table which can compete to become primary key.So all those columns that has the ability to become primary key are Alternate keys and one of them selected by the database admin as Primary key.