MySQL 5.1 英文手册 :: 11.5.1 Arithmetic Operators

MySQL 5.1 Reference Manual :: 11 Functions and Operators :: 11.5 Numeric Functions :: 11.5.1 Arithmetic Operators
11.5.1. Arithmetic Operators

Table 11.10. Arithmetic Functions

Name Description

DIV(v4.1.0) Integer division

/ Division operator

- Minus operator

% Modulo operator

+ Addition operator

* Times operator

- Change the sign of the argument

The usual arithmetic operators are available. The result is determined according to the following rules:
- In the case of -, +, and *, the result is calculated with BIGINT (64-bit) precision if both arguments are integers.
- If one of the arguments is an unsigned integer, and the other argument is also an integer, the result is an unsigned integer.
- If any of the operands of a +, -, /, *, % is a real or string value, then the precision of the result is the precision of the argument with the maximum precision.
- In division performed with /, the scale of the result when using two exact values is the scale of the first argument plus the value of the div_precision_increment system variable (which is 4 by default). For example, the result of the expression 5.05 / 0.014 has a scale of six decimal places (360.714286).
These rules are applied for each operation, such that nested calculations imply the precision of each component. Hence, (14620 / 9432456) / (24250 / 9432456), would resolve first to (0.0014) / (0.0026), with the final result having 8 decimal places (0.60288653).

Because of these rules and the way they are applied, care should be taken to ensure that components and subcomponents of a calculation use the appropriate level of precision. See Section 11.9, “Cast Functions and Operators”.

Arithmetic operators apply to numbers. For other types of values, alternative operations may be available. For example, to add date values, use DATE_ADD(); see Section 11.6, “Date and Time Functions”.
- +
  
  Addition:
```
mysql> SELECT 3+5;
        -> 8
```
- -
  
  Subtraction:
```
mysql> SELECT 3-5;
        -> -2
```
- -
  
  Unary minus. This operator changes the sign of the argument.
```
mysql> SELECT - 2;
        -> -2
```
  Note
  
  If this operator is used with a BIGINT, the return value is also a BIGINT. This means that you should avoid using - on integers that may have the value of –2⁶³.
- *
  
  Multiplication:
```
mysql> SELECT 3*5;
        -> 15
mysql> SELECT 18014398509481984*18014398509481984.0;
        -> 324518553658426726783156020576256.0
mysql> SELECT 18014398509481984*18014398509481984;
        -> 0
```
  The result of the last expression is incorrect because the result of the integer multiplication exceeds the 64-bit range of BIGINT calculations. (See Section 10.2, “Numeric Types”.)
- /
  
  Division:
```
mysql> SELECT 3/5;
        -> 0.60
```
  Division by zero produces a NULL result:
```
mysql> SELECT 102/(1-1);
        -> NULL
```
  A division is calculated with BIGINT arithmetic only if performed in a context where its result is converted to an integer.
- DIV
  
  Integer division. Similar to FLOOR(), but is safe with BIGINT values. Incorrect results may occur for noninteger operands that exceed BIGINT range.
```
mysql> SELECT 5 DIV 2;
        -> 2
```
- N % M
  
  Modulo operation. Returns the remainder of N divided by M. For more information, see the description for the MOD() function in Section 11.5.2, “Mathematical Functions”.

Name	Description
`DIV`(v4.1.0)	Integer division
`/`	Division operator
`-`	Minus operator
`%`	Modulo operator
`+`	Addition operator
`*`	Times operator
`-`	Change the sign of the argument

MySQL 实验室 因为专注，所以专业。

11.5.1. Arithmetic Operators

Note

MySQL 实验室因为专注，所以专业。