In relational database terminology, a value that does not change, such as a number or NULL, is called a ...

• A. Constant
• B. Expression
• C. DESC
• D. AVG

Answer: (A)

A constant is a fixed value written directly in a statement, such as a number or NULL, that does not depend on data in the table and does not change from row to row. In SQL, constants include numeric literals like 7, string literals like 'Alice', and NULL, which represents an unknown or missing value. They’re used to compare against column values or as fixed inputs in expressions.

An expression, by contrast, computes a value using operations and may involve column data, so it can yield different results for different rows. DESC is a sort direction keyword used in ORDER BY, not a value. AVG is an aggregate function that calculates the mean of a set of values, not a single fixed value.