what is null value?

In a relational database, a null value is used when a column's value is absent or ambiguous. A null is not a zero value or an empty string (for character or datetime data types) (for numeric data types).

The phrase used to denote a missing value in SQL is NULL. A field that seems to be empty in a table has a value of NULL.

A field with a NULL value has no value at all. Understanding the distinction between a NULL value and a zero value or a field with spaces is crucial.