## 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
Operator Purpose Example

+ -

When these denote a positive or negative expression, they are unary operators.

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

When they add or subtract, they are binary operators.

```SELECT hire_date
FROM employees
WHERE SYSDATE - hire_date
> 365;
```

* /

Multiply, divide. These are binary operators.

```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.

 See Also: "Comments" for more information on comments within SQL statements