mysql数学函数之greatest,least用法

语法

GREATEST(value1,value2,…)

With two or more arguments, returns the largest (maximum-valued) argument. The arguments are compared using the same rules as for LEAST().
使用两个或更多参数，返回最大（最大值）参数。 参数使用与LEAST()相同的规则进行比较。

LEAST(value1,value2,…)

With two or more arguments, returns the smallest (minimum-valued) argument. The arguments are compared using the following rules:
o If any argument is NULL, the result is NULL. No comparison is needed.
o If all arguments are integer-valued, they are compared as integers.
o If at least one argument is double precision, they are compared as double-precision values. Otherwise, if at least one argument is a DECIMAL value, they are compared as DECIMAL values.
o If the arguments comprise a mix of numbers and strings, they are compared as numbers.
o If any argument is a nonbinary (character) string, the arguments are compared as nonbinary strings.
o In all other cases, the arguments are compared as binary strings.
The return type of LEAST() is the aggregated type of the comparison argument types.

使用两个或更多参数，返回最小（最小值）参数。 使用以下规则比较参数：
o如果有任一参数为NULL，则结果为NULL。 不需要比较。
o如果所有参数都是整数值，则将它们作为整数进行比较。
o如果至少有一个参数是双精度，则将它们作为双精度值进行比较。 否则，如果至少有一个参数是DECIMAL值，则将它们作为DECIMAL值进行比较。
o如果参数包含数字和字符串的混合，则将它们作为数字进行比较。
o如果有任一参数是非二进制（字符）字符串，则参数将作为非二进制字符串进行比较。
o在所有其他情况下，参数将作为二进制字符串进行比较。
LEAST()的返回类型是比较参数类型的聚合类型。

实例

SELECT greatest(3,1,5,9,2,NULL);     # null
SELECT greatest(3,1,5,9,2,6);     # 9
SELECT greatest(3,1,5,9,2,6.0);     # 9.0
SELECT greatest(3,1,5,9,2,"6");     # 9

SELECT least(3,1,5,9,2,NULL);     # null
SELECT least(3,1,5,9,2,6);     # 1
SELECT least(3,1,5,9,2,6.0);     # 1.0
SELECT least(3,1,5,9,2,"6");     # 1