注意

总体标准差是总体方差的算术平方根。

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);      
  4. INSERT INTO employees VALUES(100, 'Errazuriz', '2017-07-21', 1400);
  5. INSERT INTO employees VALUES(100, 'Hartstein', '2019-05-01',14000);     
  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：

查询结果如下：

  1. +------------+-----------+--------+-------------------------------------------+
  2. | MANAGER_ID | LAST_NAME | SALARY | POP_STD                                   |
  3. +------------+-----------+--------+-------------------------------------------+
  4. |        100 | De Haan   |  11000 | 5637.250548804798333699350384281939588505 |
  5. |        100 | Errazuriz |   1400 | 5637.250548804798333699350384281939588505 |
  6. |        100 | Hartstein |  14000 | 5637.250548804798333699350384281939588505 |
  8. |        100 | Raphaely  |   1700 | 5637.250548804798333699350384281939588505 |
  9. |        100 | Russell   |  13000 | 5637.250548804798333699350384281939588505 |
  10. |        100 | Weiss     |  13500 | 5637.250548804798333699350384281939588505 |
  11. |        200 | Bell      |  13000 |  408.248290463863016366214012450981899069 |
  12. |        200 | Part      |  14000 |  408.248290463863016366214012450981899069 |
  13. |        200 | Ross      |  13500 |  408.248290463863016366214012450981899069 |
  14. +------------+-----------+--------+-------------------------------------------+

聚合函数示例

查询结果如下：

  1. +-------------------------------------------+
  2. | STDDEV_POP(SALARY)                        |
  3. +-------------------------------------------+
  4. | 5249.950806538512715446505486136315088416 |