MySQL的SQRT()函式是用來找出任何數的平方根。使用SELECT語句來查詢出任何數的平方根如下：
mysql> select SQRT(16); +----------+ | SQRT(16) | +----------+ | 4.000000 | +----------+ 1 row in set (0.00 sec)
在這裡所看到的浮點值，是MySQL的內部操作平方根以浮點資料型別返回。
也可以使用Sqrt()函式找出各種記錄平方根。要理解更詳細Sqrt()函式，考慮anemployee_tbl表，其具有以下記錄：
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)
假設在上表基礎上，要計算所有dialy_typing_pages列的值的平方根，那麼可以使用下面的命令：
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)