Syntax
STDDEV_SAMP(expr)
Purpose
STDDEV_SAMP() returns the sample standard deviation of expr. The result returned by this function is the square root of the result returned by the VAR_SAMP() function. For more information about VAR_SAMP(), see VAR_SAMP.
If no matching row is found, it returns NULL.
Examples
obclient> CREATE TABLE employees (manager_id INT, last_name VARCHAR(50), hiredate VARCHAR(50), salary INT);
INSERT INTO employees VALUES(100, 'Raphaely', '2017-07-01', 1700);
INSERT INTO employees VALUES(100, 'De Haan', '2018-05-01',11000);
INSERT INTO employees VALUES(100, 'Errazuriz', '2017-07-21', 1400);
INSERT INTO employees VALUES(100, 'Hartstein', '2019-05-01',14000);
INSERT INTO employees VALUES(100, 'Raphaely', '2017-07-22', 1700);
INSERT INTO employees VALUES(100, 'Weiss', '2019-07-11',13500);
INSERT INTO employees VALUES(100, 'Russell', '2019-10-05', 13000);
INSERT INTO employees VALUES(100, 'Partners', '2018-12-01',14000);
INSERT INTO employees VALUES(200, 'Ross', '2019-06-11',13500);
INSERT INTO employees VALUES(200, 'Bell', '2019-05-25', 13000);
INSERT INTO employees VALUES(200, 'Part', '2018-08-11',14000);
COMMIT;
obclient> SELECT STDDEV_SAMP(salary) FROM employees;
+---------------------+
| STDDEV_SAMP(salary) |
+---------------------+
| 5506.194858355616 |
+---------------------+
1 row in set