Oracle® Database SQL Reference 10g Release 1 (10.1) Part Number B1075901 


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You can use an arithmetic operator with one or two arguments to negate, add, subtract, multiply, and divide numeric values. Some of these operators are also used in datetime and interval arithmetic. The arguments to the operator must resolve to numeric datatypes or to any datatype that can be implicitly converted to a numeric datatype.
Unary arithmetic operators return the same datatype as the numeric datatype of the argument. For binary arithmetic operators, Oracle determines the argument with the highest numeric precedence, implicitly converts the remaining arguments to that datatype, and returns that datatype. Table 42 lists arithmetic operators.
See Also: Table 211, "Implicit Type Conversion Matrix" for more information on implicit conversion, "Numeric Precedence " for information on numeric precedence, and "Datetime/Interval Arithmetic " 
Table 42 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 parentheses. Please refer to "Comments " for more information on comments within SQL statements.