絕對值函數ABS(x)和圓周率函數PI()

復制代碼 代碼如下:

mysql> SELECT ABS(0.5), ABS(-0.5), PI();

+----------+-----------+----------+

| ABS(0.5) | ABS(-0.5) | PI()???? |

+----------+-----------+----------+

|????? 0.5 |?????? 0.5 | 3.141593 |

+----------+-----------+----------+

row in set (0.00 sec)

平方根函數SQRT(x)和求余函數MOD(x,y)

復制代碼 代碼如下:

mysql> SELECT SQRT(16), SQRT(3), MOD(13,4);

+----------+--------------------+-----------+

| SQRT(16) | SQRT(3)??????????? | MOD(13,4) |

+----------+--------------------+-----------+

|??????? 4 | 1.7320508075688772 |???????? 1 |

+----------+--------------------+-----------+

row in set (0.00 sec)

取整函數CEIL(x)、CEILING(x)和FLOOR(x)

復制代碼 代碼如下:

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 |

+-----------+------------+--------------+---------------+

row in set (0.00 sec)

mysql> SELECT FLOOR(2.3), FLOOR(-2.3);

+------------+-------------+

| FLOOR(2.3) | FLOOR(-2.3) |

+------------+-------------+

|????????? 2 |????????? -3 |

+------------+-------------+

row in set (0.00 sec)

CEIL(x)和CEILING(x)返回大于或等于x的最小整數

FLOOR(x)返回小于或等于x的最大整數

隨機數函數RAND()和RAND(x)

復制代碼 代碼如下:

mysql> SELECT RAND(), RAND(2), RAND(2);

+--------------------+--------------------+--------------------+

| RAND()???????????? | RAND(2)??????????? | RAND(2)??????????? |

+--------------------+--------------------+--------------------+

| 0.8269294489425881 | 0.6555866465490187 | 0.6555866465490187 |

+--------------------+--------------------+--------------------+

row in set (0.00 sec)

RAND()和RAND(x)這兩個函數丟失返回0～1的隨機數

區別在于，RAND()返回的數是完全隨機的，而RAND(x)在x相同時返回的值相同

四舍五入函數ROUND(x)、ROUND(x,y)和TRUNCATE(x,y)

復制代碼 代碼如下:

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 |

+------------+------------+---------------+---------------+

row in set (0.00 sec)

ROUND(x)返回離x最近的整數，也就是對x進行四舍五入處理

ROUND(x,y)返回x保留到小數點后y位的值，在截取時進行四舍五入處理

復制代碼 代碼如下:

mysql> SELECT TRUNCATE(2.53,1), TRUNCATE(2.55,1);

+------------------+------------------+

| TRUNCATE(2.53,1) | TRUNCATE(2.55,1) |

+------------------+------------------+

|????????????? 2.5 |????????????? 2.5 |

+------------------+------------------+

row in set (0.00 sec)

TRUNCATE(x,y)返回x保留到小數點后y位的值，不進行四舍五入操作

符號函數SIGN(x)

復制代碼 代碼如下:

mysql> SELECT SIGN(-2), SIGN(0), SIGN(2);

+----------+---------+---------+

| SIGN(-2) | SIGN(0) | SIGN(2) |

+----------+---------+---------+

|?????? -1 |?????? 0 |?????? 1 |

+----------+---------+---------+

row in set (0.00 sec)

SIGN(x)返回x的符號，-1為負數，0不變，1為整數

冪運算函數POW(x,y)、POWER(x,y)

復制代碼 代碼如下:

mysql> SELECT POW(3,2), POWER(3,2);

+----------+------------+

| POW(3,2) | POWER(3,2) |

+----------+------------+

|??????? 9 |????????? 9 |

+----------+------------+

row in set (0.00 sec)

總結

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