A monadic arithmetic operator performs a mathematical operation on a single numeric operand to produce a result. The - (negation) operator changes the sign of its operand, and the not very useful + (identity) operator leaves its operand unchanged. A dyadic arithmetic operator performs a mathematical operation on two numeric operands to produce a result. These operators include the usual ones: + (addition), - (subtraction), * (multiplication), and / (division). Table 5.1 lists SQL’s arithmetic operators (expr is a numeric expression).