Null is a special marker utilized in structured query language to demonstrate that a data value does not exist in the database.
Null strives to fulfill the requirement that all the relational database management systems support a representation of missing information.
• A null value in a spread sheet is a value in an area that happens to be empty.
• A field with a null value has a zero value.
• If a column in a table is discretionary, we can introduce a new record or fill in an existing record without adding a value to this column.
• Null represents the absence of a value, so null is never greater than or less than another value.
• It is an item returned when an expression or function results in an undefined value.