MySQL的SQRT函数是用来计算出任何数量的平方根。可以使用SELECT语句找出方检定根的任意数如下:
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mysql> select SQRT(16); + ----------+ | SQRT(16) | + ----------+ | 4.000000 | + ----------+ 1 row in set (0.00 sec) |
所看到的浮点值,因为内部MySQL将处理浮点数据类型的平方根。
可以使用SQRT函数,计算出记录的平方根。了解SQRT函数更详细用法,考虑EMPLOYEE_TBL的表具有以下记录:
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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) |
假设根据上面的表格,要计算所有的dialy_typing_pages的平方根,然后可以通过使用下面的命令:
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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) |