MySQL SQRT 函数

  • SQRT 函数

    MySQL SQRT函数用于找出任何数字的平方根。您可以使用SELECT语句找出任何数字的平方根,如下所示:
    mysql>  select SQRT(16);
    +----------+
    | SQRT(16) |
    +----------+
    | 4.000000 |
    +----------+
    1 row in set (0.00 sec)
    
    您在这里看到的是float值,因为MySQL内部会在float数据类型中操纵平方根。您也可以使用SQRT函数找出各种记录的平方根。为了更详细地了解SQRT函数,请考虑一个employee_tbl表,该表具有以下记录
    mysql> SELECT * FROM employee_tbl;
    +------+------+------------+--------------------+
    |  id  | name | work_date  | daily_typing_pages |
    +------+------+------------+--------------------+
    |   1  | John | 2007-01-24 |        250         |
    |   2  | Ram  | 2007-05-27 |        220         |
    |   3  | Jack | 2007-05-06 |        170         |
    |   3  | Jack | 2007-04-06 |        100         |
    |   4  | Jill | 2007-04-06 |        220         |
    |   5  | Zara | 2007-06-06 |        300         |
    |   5  | Zara | 2007-02-06 |        350         |
    +------+------+------------+--------------------+
    7 rows in set (0.00 sec)
    现在,假设基于上表您要计算所有dialy_typing_pages的平方根,那么可以使用以下命令执行此操作:
    mysql> SELECT name, SQRT(daily_typing_pages)
       -> FROM employee_tbl;
    +------+--------------------------+
    | name | SQRT(daily_typing_pages) |
    +------+--------------------------+
    | John |         15.811388        |
    | Ram  |         14.832397        |
    | Jack |         13.038405        |
    | Jack |         10.000000        |
    | Jill |         14.832397        |
    | Zara |         17.320508        |
    | Zara |         18.708287        |
    +------+--------------------------+
    7 rows in set (0.00 sec)