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。要更详细地了解 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,那么您可以使用以下命令执行以下操作:
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)
