Engineer's Day is celebrated on the birth anniversary of Sir Mokshagundam Visvesvaraya in the memory of his contributions in engineering. Every year on his birthday i.e, on September 15 National Engineers Day is celebrated all over the country.
A candidate key is a column, or set of columns, in a table that can uniquely identify any database record without referring to any other data. Each table may have one or more candidate keys, but one candidate key is unique, and it is called the primary key.