SQL SQRT函數(shù)用來找出任何數(shù)的平方根。您可以使用SELECT語句來找出任何數(shù)的平方根如下:
SQL> select SQRT(16); +----------+ | SQRT(16) | +----------+ | 4.000000 | +----------+ 1 row in set (0.00 sec)
你所看到的是浮點值,因為在這里SQL內(nèi)部操縱會平方根浮點數(shù)據(jù)類型。
可以使用SQRT函數(shù)來計算各種記錄的平方根。理解SQRT函數(shù)更加詳細考慮employee_tbl表,其由具有以下記錄:
SQL> 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)
現(xiàn)在假設(shè)基于上述表要計算全部dialy_typing_pages的平方根, 那么你可以使用以下命令:
SQL> 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)