Define alternate key. There can be a key apart from primary key in a table that can also be a key. This key may or may not be a unique key. For example, in an employee table, empno is a primary key, empname is a alternate key that may not be unique but still helps in identifying a row of the table.
Define alternate key.An alternate key is similar to a primary key. It accepts null values; where as the primary key does not. The null values can be submitted to the attribute in a tuple.