MysqL之数值函数

1.CEIL()

用法：向上取整

举例：

mysql> select CEIL(3.5);
+-----------+
| CEIL(3.5) |
+-----------+
|         4 |
+-----------+
1 row in set (0.05 sec)

mysql> select CEIL(3.1);
+-----------+
| CEIL(3.1) |
+-----------+
|         4 |
+-----------+
1 row in set (0.00 sec)

mysql> select CEIL(3.0);
+-----------+
| CEIL(3.0) |
+-----------+
|         3 |
+-----------+
1 row in set (0.00 sec)

2.DIV（DIV(X,Y)）

用法：数字除法，除数不能为0

举例：

mysql> select 3 DIV 4;
+---------+
| 3 DIV 4 |
+---------+
|       0 |
+---------+
1 row in set (0.03 sec)

mysql> select 3 DIV 4.0;
+-----------+
| 3 DIV 4.0 |
+-----------+
|         0 |
+-----------+
1 row in set (0.00 sec)

mysql> select 3.3 DIV 4;
+-----------+
| 3.3 DIV 4 |
+-----------+
|         0 |
+-----------+
1 row in set (0.00 sec)

mysql> select 4.3 DIV 4;
+-----------+
| 4.3 DIV 4 |
+-----------+
|         1 |
+-----------+
1 row in set (0.00 sec)

3.FLOOR()

用法：向下取整（可以使正数可以使负数）

举例：

mysql> select FLOOR(2.3);
+------------+
| FLOOR(2.3) |
+------------+
|          2 |
+------------+
1 row in set (0.00 sec)

mysql> select FLOOR(2.0);
+------------+
| FLOOR(2.0) |
+------------+
|          2 |
+------------+
1 row in set (0.00 sec)

mysql> select FLOOR(-2.3);
+-------------+
| FLOOR(-2.3) |
+-------------+
|          -3 |
+-------------+
1 row in set (0.00 sec)

4.MOD(MOD(X,Y))

用法：取余数（可以是正数可以是余数）

举例：

mysql> select 3 MOD 4;
+---------+
| 3 MOD 4 |
+---------+
|       3 |
+---------+
1 row in set (0.00 sec)

mysql> select -3 MOD 4;
+----------+
| -3 MOD 4 |
+----------+
|       -3 |
+----------+
1 row in set (0.00 sec)

mysql> select -5 MOD 4;
+----------+
| -5 MOD 4 |
+----------+
|       -1 |
+----------+
1 row in set (0.00 sec)

mysql> select 5 MOD 4;
+---------+
| 5 MOD 4 |
+---------+
|       1 |
+---------+
1 row in set (0.00 sec)

5.POEWE()

用法：幂运算

举例：

mysql> select POWER(2,3);
+------------+
| POWER(2,3) |
+------------+
|          8 |
+------------+
1 row in set (0.03 sec)

mysql> select POWER(2,-3);
+-------------+
| POWER(2,-3) |
+-------------+
|       0.125 |
+-------------+
1 row in set (0.00 sec)

mysql> select POWER(2,2.2);
+------------------+
| POWER(2,2.2)     |
+------------------+
| 4.59479341998814 |
+------------------+
1 row in set (0.03 sec)

6.ROUND()

用法：四舍五入

举例：

mysql> select ROUND(3.4);
+------------+
| ROUND(3.4) |
+------------+
|          3 |
+------------+
1 row in set (0.01 sec)

mysql> select ROUND(3.5);
+------------+
| ROUND(3.5) |
+------------+
|          4 |
+------------+
1 row in set (0.00 sec)

mysql> select ROUND(-3.5);
+-------------+
| ROUND(-3.5) |
+-------------+
|          -4 |
+-------------+
1 row in set (0.00 sec)

7.TRUNCATE()

用法：数字截取（和正负数没有关系，只是截取位数）

举例：

mysql> select TRUNCATE(2.343434,3);
+----------------------+
| TRUNCATE(2.343434,3) |
+----------------------+
|                2.343 |
+----------------------+
1 row in set (0.00 sec)

mysql> select TRUNCATE(2.343934,3);
+----------------------+
| TRUNCATE(2.343934,3) |
+----------------------+
|                2.343 |
+----------------------+
1 row in set (0.00 sec)

mysql> select TRUNCATE(-2.343934,3);
+-----------------------+
| TRUNCATE(-2.343934,3) |
+-----------------------+
|                -2.343 |
+-----------------------+
1 row in set (0.00 sec)

8.ABS()

用法：返回绝对值

举例：

mysql> select ABS(2);
+--------+
| ABS(2) |
+--------+
|      2 |
+--------+
1 row in set (0.03 sec)

mysql> select ABS(-2);
+---------+
| ABS(-2) |
+---------+
|       2 |
+---------+
1 row in set (0.00 sec)

9.SIGN()

用法：返回符号（-1,0，1）

举例：

mysql> select SIGN(2)
    -> ;
+---------+
| SIGN(2) |
+---------+
|       1 |
+---------+
1 row in set (0.00 sec)

mysql> select SIGN(-2)
    -> ;
+----------+
| SIGN(-2) |
+----------+
|       -1 |
+----------+
1 row in set (0.00 sec)

mysql> select SIGN(0);
+---------+
| SIGN(0) |
+---------+
|       0 |
+---------+
1 row in set (0.00 sec)

10.SQRT(N)

用法：求N的平方根

举例：

mysql> select SQRT(4);
+---------+
| SQRT(4) |
+---------+
|       2 |
+---------+
1 row in set (0.00 sec)

mysql> select SQRT(3);
+--------------------+
| SQRT(3)            |
+--------------------+
| 1.7320508075688772 |
+--------------------+
1 row in set (0.00 sec)

11.SIN(),TAN(),COS(),ACOS(),ASIN(),ATAN(),COT(),ASCOT()

用法：数学的三角函数

举例：

mysql> select SIN(30);
+---------------------+
| SIN(30)             |
+---------------------+
| -0.9880316240928618 |
+---------------------+
1 row in set (0.00 sec)

mysql> select SIN(PI());
+------------------------+
| SIN(PI())              |
+------------------------+
| 1.2246467991473532e-16 |
+------------------------+
1 row in set (0.00 sec)

12.DEGREES(N),RADIANS(N)

用法：把N从弧度变换为角度并返回（把N从角度变换为弧度并返回）

举例：

mysql> select DEGREES(PI());
+---------------+
| DEGREES(PI()) |
+---------------+
|           180 |
+---------------+
1 row in set (0.00 sec)

mysql> select RADIANS(180);
+-------------------+
| RADIANS(180)      |
+-------------------+
| 3.141592653589793 |
+-------------------+
1 row in set (0.00 sec)

13.LEAST(),GREATEST()

用法：返回最大值最小值

举例：

mysql> select LEAST(3,1,4,6,-1);
+-------------------+
| LEAST(3,1,4,6,-1) |
+-------------------+
|                -1 |
+-------------------+
1 row in set (0.00 sec)

mysql> select LEAST("B","A","C");
+--------------------+
| LEAST("B","A","C") |
+--------------------+
| A                  |
+--------------------+
1 row in set (0.00 sec)

mysql> select GREATEST("B","A","C");
+-----------------------+
| GREATEST("B","A","C") |
+-----------------------+
| C                     |
+-----------------------+
1 row in set (0.00 sec)

mysql> select GREATEST(2,4,5);
+-----------------+
| GREATEST(2,4,5) |
+-----------------+
|               5 |
+-----------------+
1 row in set (0.00 sec)