Arithmetic Operators

You can use an arithmetic operator in an expression to negate, add, subtract, multiply, and divide numeric values. The result of the operation is also a numeric value. Some of these operators are also used in date arithmetic. Table 3-2 lists arithmetic operators.

Table 3-2 Arithmetic Operators

SELECT * FROM order_items
 WHERE quantity = -1;
SELECT * FROM employees
  WHERE -salary < 0;

SELECT hire_date 
  FROM employees
  WHERE SYSDATE - hire_date
  > 365;

UPDATE employees
  SET salary = salary * 1.1;

Do not use two consecutive minus signs (--) in arithmetic expressions to indicate double negation or the subtraction of a negative value. The characters -- are used to begin comments within SQL statements. You should separate consecutive minus signs with a space or a parenthesis.