Why is Null used in nullable columns?

Why is Null used in nullable columns?

• A. To indicate data is complete
• B. To represent explicitly zero values
• C. To avoid giving the impression that information is missing
• D. To speed up queries

Answer: (C)

Null marks the absence of a value in a column that can be empty. It signals that for this row and field there is no data, whether it wasn’t provided yet or isn’t applicable. This distinction is important because treating a missing value as zero or as an empty string would mislead analyses and calculations. Using Null keeps the data honest about whether information exists, and it forces explicit handling in queries (for example, checking for Null with IS NULL or supplying a default with COALESCE) rather than assuming a value is present. The other ideas—that a value is complete, that a zero is meant, or that performance is improved—don’t capture that Null is about the intentional absence of information.

Null marks the absence of a value in a column that can be empty. It signals that for this row and field there is no data, whether it wasn’t provided yet or isn’t applicable. This distinction is important because treating a missing value as zero or as an empty string would mislead analyses and calculations. Using Null keeps the data honest about whether information exists, and it forces explicit handling in queries (for example, checking for Null with IS NULL or supplying a default with COALESCE) rather than assuming a value is present. The other ideas—that a value is complete, that a zero is meant, or that performance is improved—don’t capture that Null is about the intentional absence of information.