MySQL中的数学函数

1. bin

将十进制数值转换为二进制数值。

MariaDB [test]> select bin(11);
+---------+
| bin(11) |
+---------+
| 1011    |
+---------+

2. ceiling

进一法取整。

MariaDB [test]> select ceiling(3.2);
+--------------+
| ceiling(3.2) |
+--------------+
|            4 |
+--------------+

3. floor

舍去法取整。

MariaDB [test]> select floor(3.2);
+------------+
| floor(3.2) |
+------------+
|          3 |
+------------+

4. round

四舍五入取整。

MariaDB [test]> select round(3.3), round(3.5);
+------------+------------+
| round(3.3) | round(3.5) |
+------------+------------+
|          3 |          4 |
+------------+------------+

5. truncate

截取浮点数，第二个参数指定保留的小数位数。

MariaDB [test]> select truncate(3.1415926, 2), truncate(3.1415926, 4);
+------------------------+------------------------+
| truncate(3.1415926, 2) | truncate(3.1415926, 4) |
+------------------------+------------------------+
|                   3.14 |                 3.1415 |
+------------------------+------------------------+

6. format

对数值进行千分位格式化，第二个参数指定保留的小数位数（会进行四舍五入）。

MariaDB [test]> select format(3150.46358, 2), format(3150.46358, 3);
+-----------------------+-----------------------+
| format(3150.46358, 2) | format(3150.46358, 3) |
+-----------------------+-----------------------+
| 3,150.46              | 3,150.464             |
+-----------------------+-----------------------+
1 row in set (0.00 sec)

7. max

取最大值。

8. min

取最小值。

9. sum

求和。

10. sign

返回数值的符号。（负数返回-1，0返回0，正数返回1）

MariaDB [test]> select sign(-3), sign(0), sign(3);
+----------+---------+---------+
| sign(-3) | sign(0) | sign(3) |
+----------+---------+---------+
|       -1 |       0 |       1 |
+----------+---------+---------+

11. power

幂运算。

MariaDB [test]> select sign(-3), sign(0), sign(3);
+----------+---------+---------+
| sign(-3) | sign(0) | sign(3) |
+----------+---------+---------+
|       -1 |       0 |       1 |
+----------+---------+---------+

12. sqrt

求平方根。

MariaDB [test]> select sqrt(9), sqrt(64);
+---------+----------+
| sqrt(9) | sqrt(64) |
+---------+----------+
|       3 |        8 |
+---------+----------+

13. rand

返回0~1之间的随机数。

MariaDB [test]> select rand(), rand();
+--------------------+--------------------+
| rand()             | rand()             |
+--------------------+--------------------+
| 0.6072439082034341 | 0.7944739868812952 |
+--------------------+--------------------+