mysql随机函数结果

绝对值函数ABS(x)和圆周率函数PI()复制代码mysql> ｓｅｌｅｃｔ ABS(0.5), ABS(-0.5), PI();+----------+-----------+----------+| ABS(0.5) | ABS(-0.5) | PI() |+----------+-----------+----------+|0.5 |0.5 | 3.141593 |+----------+-----------+----------+1 row in set (0.00 sec)复制代码 平方根函数SQRT(x)和求余函数MOD(x,y)复制代码mysql> ｓｅｌｅｃｔ SQRT(16), SQRT(3), MOD(13,4);+----------+--------------------+-----------+| SQRT(16) | SQRT(3)| MOD(13,4) |+----------+--------------------+-----------+|4 | 1.7320508075688772 | 1 |+----------+--------------------+-----------+1 row in set (0.00 sec)复制代码 取整函数CEIL(x)、CEILING(x)和FLOOR(x)复制代码mysql> ｓｅｌｅｃｔ CEIL(2.3), CEIL(-2.3), CEILING(2.3), CEILING(-2.3);+-----------+------------+--------------+---------------+| CEIL(2.3) | CEIL(-2.3) | CEILING(2.3) | CEILING(-2.3) |+-----------+------------+--------------+---------------+| 3 | -2 |3 |-2 |+-----------+------------+--------------+---------------+1 row in set (0.00 sec)mysql> ｓｅｌｅｃｔ FLOOR(2.3), FLOOR(-2.3);+------------+-------------+| FLOOR(2.3) | FLOOR(-2.3) |+------------+-------------+|2 |-3 |+------------+-------------+CEIL(x)和CEILING(x)返回大于或等于x的最小整数FLOOR(x)返回小于或等于x的最大整数 随机数函数RAND()和RAND(x)mysql> ｓｅｌｅｃｔ RAND(), RAND(2), RAND(2);+--------------------+--------------------+--------------------+| RAND() | RAND(2)| RAND(2)|+--------------------+--------------------+--------------------+| 0.8269294489425881 | 0.6555866465490187 | 0.6555866465490187 |+--------------------+--------------------+--------------------+1 row in set (0.00 sec)RAND()和RAND(x)这两个函数丢失返回0～1的随机数区别在于，RAND()返回的数是完全随机的，而RAND(x)在x相同时返回的值相同 四舍五入函数ROUND(x)、ROUND(x,y)和ｔｒｕｎｃａｔｅ(x,y)mysql> ｓｅｌｅｃｔ ROUND(2.3), ROUND(2.5), ROUND(2.53,1), ROUND(2.55,1);+------------+------------+---------------+---------------+| ROUND(2.3) | ROUND(2.5) | ROUND(2.53,1) | ROUND(2.55,1) |+------------+------------+---------------+---------------+|2 |3 |2.5 |2.6 |+------------+------------+---------------+---------------+1 row in set (0.00 sec)ROUND(x)返回离x最近的整数，也就是对x进行四舍五入处理ROUND(x,y)返回x保留到小数点后y位的值，在截取时进行四舍五入处理mysql> ｓｅｌｅｃｔ ｔｒｕｎｃａｔｅ(2.53,1), ｔｒｕｎｃａｔｅ(2.55,1);+------------------+------------------+| ｔｒｕｎｃａｔｅ(2.53,1) | ｔｒｕｎｃａｔｅ(2.55,1) |+------------------+------------------+|2.5 |2.5 |+------------------+------------------+1 row in set (0.00 sec)ｔｒｕｎｃａｔｅ(x,y)返回x保留到小数点后y位的值，不进行四舍五入操作 符号函数SIGN(x)mysql> ｓｅｌｅｃｔ SIGN(-2), SIGN(0), SIGN(2);+----------+---------+---------+| SIGN(-2) | SIGN(0) | SIGN(2) |+----------+---------+---------+|-1 |0 |1 |+----------+---------+---------+1 row in set (0.00 sec)SIGN(x)返回x的符号，-1为负数，0不变，1为整数 幂运算函数POW(x,y)、POWER(x,y)mysql> ｓｅｌｅｃｔ POW(3,2), POWER(3,2);+----------+------------+| POW(3,2) | POWER(3,2) |+----------+------------+|9 |9 |+----------+------------+1 row in set (0.00 sec)