Calculate population standard deviation. This function is a synonym for STD() and STDDEV_POP(), returning the square root of the population variance.
STDDEV(expr)Returns the population standard deviation of expr. This function is provided for compatibility with Oracle. The standard SQL function can be used instead.
It is an , and so can be used with the clause.
STDDEV() can be used as a .
This function returns NULL if there were no matching rows.
As an :
As a :
(equivalent, standard SQL)
(equivalent, non-standard SQL)
(variance)
(sample standard deviation)
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CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, STDDEV_POP(score)
OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name | test | score | stddev_results |
+---------+--------+-------+----------------+
| Chun | SQL | 75 | 16.9466 |
| Chun | Tuning | 73 | 24.1247 |
| Esben | SQL | 43 | 16.9466 |
| Esben | Tuning | 31 | 24.1247 |
| Kaolin | SQL | 56 | 16.9466 |
| Kaolin | Tuning | 88 | 24.1247 |
| Tatiana | SQL | 87 | 16.9466 |
+---------+--------+-------+----------------+