How I Learned to Stop Worrying and Love NULL in SQL
The NULL value is a data type that represents an unknown value. It is not equivalent to empty string or zero. Suppose you have an employee table containing columns such as EmployeeId
, Name
, ContactNumber
and an alternate contact number. This table has a few mandatory value columns like EmployeeId
, Name
, and ContactNumber
. However, an alternate contact number is not required and therefore has an…