| --- | |
| { | |
| "title": "STD,STDDEV,STDDEV_POP", | |
| "language": "en", | |
| "description": "Returns the standard deviation of the expr expression" | |
| } | |
| --- | |
| ## Description | |
| Returns the standard deviation of the expr expression | |
| ## Alias | |
| - STD | |
| - STDDEV_POP | |
| ## Syntax | |
| ```sql | |
| STDDEV(<expr>) | |
| ``` | |
| ## Parameters | |
| | Parameter | Description | | |
| | -- | -- | | |
| | `<expr>` | The value to be calculated standard deviation, supports type Double. | | |
| ## Return Value | |
| Return the population standard deviation of the expr expression as Double type. | |
| If there is no valid data in the group, returns NULL. | |
| ## Examples | |
| ```sql | |
| -- Create sample tables | |
| CREATE TABLE score_table ( | |
| student_id INT, | |
| score DOUBLE | |
| ) DISTRIBUTED BY HASH(student_id) | |
| PROPERTIES ( | |
| "replication_num" = "1" | |
| ); | |
| -- Insert test data | |
| INSERT INTO score_table VALUES | |
| (1, 85), | |
| (2, 90), | |
| (3, 82), | |
| (4, 88), | |
| (5, 95); | |
| -- Calculate the standard deviation of all students' scores | |
| SELECT STDDEV(score) as score_stddev | |
| FROM score_table; | |
| ``` | |
| ```text | |
| +-------------------+ | |
| | score_stddev | | |
| +-------------------+ | |
| | 4.427188724235729 | | |
| +-------------------+ | |
| ``` |