说明

样本标准差是样本方差的算术平方根。

作为分析函数使用时，您需要使用窗口函数的完整语法，它对一组行的集合进行计算并返回多个值 。作为聚合函数使用时，该函数对一组行的集合进行聚合计算，结果只能返回一个值，此时不需要加 OVER 关键字。

分析函数示例

以下语句创建了表 employees，并向里面插入数据：

  1. CREATE TABLE employees (manager_id INT,last_name varchar(50),hiredate varchar(50),SALARY INT);
  2. INSERT INTO employees VALUES(100, 'Raphaely', '2017-07-01', 1700);
  3. INSERT INTO employees VALUES(100, 'De Haan', '2018-05-01',11000);      
  5. INSERT INTO employees VALUES(100, 'Hartstein', '2019-05-01',14000);     
  6. INSERT INTO employees VALUES(100, 'Raphaely', '2017-07-22', 1700);
  7. INSERT INTO employees VALUES(100, 'Weiss',  '2019-07-11',13500);     
  8. INSERT INTO employees VALUES(100, 'Russell', '2019-10-05', 13000);
  9. INSERT INTO employees VALUES(200, 'Ross',  '2019-06-11',13500);     
  10. INSERT INTO employees VALUES(200, 'Bell', '2019-05-25', 13000);
  11. INSERT INTO employees VALUES(200, 'Part',  '2018-08-11',14000);
  12. COMMIT;

调用函数并执行以下语句：

返回结果如下：

  1. +------------+-----------+------------+--------+-------------------------------------------+
  2. | MANAGER_ID | LAST_NAME | HIREDATE   | SALARY | CUM_SDEV                                  |
  3. +------------+-----------+------------+--------+-------------------------------------------+
  4. |        100 | De Haan   | 2018-05-01 |  11000 | 4702.127178203498995615489088200868644482 |
  6. |        100 | Hartstein | 2019-05-01 |  14000 | 6340.346993658943269176828928801701088079 |
  7. |        100 | Partners  | 2018-12-01 |  14000 | 6064.899009876421676804205219406952308814 |
  8. |        100 | Raphaely  | 2017-07-22 |   1700 |  173.205080756887729352744634150587236694 |
  9. |        100 | Russell   | 2019-10-05 |  13000 | 6026.474330580265330900400184969999384459 |
  10. |        100 | Weiss     | 2019-07-11 |  13500 | 6244.311697171159907069428668980211861012 |
  11. |        200 | Bell      | 2019-05-25 |  13000 |  707.106781186547524400844362104849039285 |
  12. |        200 | Part      | 2018-08-11 |  14000 |                                      NULL |
  13. |        200 | Ross      | 2019-06-11 |  13500 |                                       500 |
  14. +------------+-----------+------------+--------+-------------------------------------------+

聚合函数示例

查询结果如下：

  1. +-------------------------------------------+
  2. | STDDEV_SAMP(SALARY)                       |
  3. +-------------------------------------------+