3 数学函数

ABS (number2 )                 //绝对值
BIN (decimal_number )             //十进制转二进制
CEILING (number2 )                 //向上取整
CONV(number2,from_base,to_base) //进制转换
FLOOR (number2 ) //向下取整
FORMAT (number,decimal_places ) //保留小数位数
HEX (DecimalNumber )             //转十六进制
注：HEX()中可传入字符串，则返回其ASC-11码，如HEX(’DEF’)返回4142143
也可以传入十进制整数，返回其十六进制编码，如HEX(25)返回19

LEAST (number , number2  [,..]) //求最小值
MOD (numerator ,denominator )     //求余
POWER (number ,power )             //求指数
RAND([seed])                         //随机数
ROUND (number  [,decimals ])     //四舍五入,decimals为小数位数]

mysql> select round(1.23); 
+————-+ 
| round(1.23) | 
+————-+ 
| 1 | 
+————-+ 
1 row in set (0.00 sec) 
mysql> select round(1.56); 
+————-+ 
| round(1.56) | 
+————-+ 
| 2 | 
+————-+ 
1 row in set (0.00 sec) 

(2)可以设定小数位数，返回浮点型数据

mysql> select round(1.567,2);
+—————-+
| round(1.567,2) |
+—————-+
|           1.57 |
+—————-+
1 row in set (0.00 sec)

SIGN (number2 )                     //返回符号,正负或0
SQRT(number2)                     //开平方