MySQL数学函数简明总结

mysql> select FLOOR(-3.35), FLOOR(3.35);
+--------------+-------------+
| FLOOR(-3.35) | FLOOR(3.35) |
+--------------+-------------+
|           -4 |           3 |
+--------------+-------------+

8. RAND()和RAND(X)

RAND(X) 返回一个随机浮点值，范围在０～１之间，X为整数，它被称作种子值，用来产生重复序列。即当Ｘ值相同时，产生的随机数也相同；

mysql> select RAND(10), RAND(10), RAND(2), RAND(-2);
+--------------------+--------------------+--------------------+--------------------+
| RAND(10)           | RAND(10)           | RAND(2)            | RAND(-2)           |
+--------------------+--------------------+--------------------+--------------------+
| 0.6570515219653505 | 0.6570515219653505 | 0.6555866465490187 | 0.6548542125661431 |
+--------------------+--------------------+--------------------+--------------------+

RAND(): 不带参数的RAND()每次产生不同０～１之间的随机数

mysql> SELECT RAND(), RAND(), RAND();
+--------------------+--------------------+---------------------+
| RAND()             | RAND()             | RAND()              |
+--------------------+--------------------+---------------------+
| 0.6931893636409094 | 0.5147262984092592 | 0.49406343185721285 |
+--------------------+--------------------+---------------------+

9. ROUND(X)和ROUND(X,Y): 四舍五入函数，对Ｘ值按照Ｙ进行四舍五入，Ｙ可以省略，默认值为０;若Ｙ不为０，则保留小数点后面指定Ｙ位。

mysql> select ROUND(-1.14), ROUND(-1.9), ROUND(1.14), ROUND(1.9);
+--------------+-------------+-------------+------------+
| ROUND(-1.14) | ROUND(-1.9) | ROUND(1.14) | ROUND(1.9) |
+--------------+-------------+-------------+------------+
|           -1 |          -2 |           1 |          2 |
+--------------+-------------+-------------+------------+

mysql> select ROUND(1.38,1), ROUND(1.38,0), ROUND(232.38,-1), ROUND(232.38,-2);
+---------------+---------------+------------------+------------------+
| ROUND(1.38,1) | ROUND(1.38,0) | ROUND(232.38,-1) | ROUND(232.38,-2) |
+---------------+---------------+------------------+------------------+
|           1.4 |             1 |              230 |              200 |
+---------------+---------------+------------------+------------------+