# STDDEV

Returns the standard deviation of all the values in a specified expression.

May be used as a window function and with the frame clause.

## Syntax

## Aggregate Function

```sql
STDDEV( [ DISTINCT ] <expression> 
```

## Window Function & Window Frame Clause

```sql
STDDEV( [DISTINCT ] (col | expr ) OVER ( [ PARTITION BY (col | expr )] [ ORDER BY (col | expr ) [ <window_frame> ] ] )
```

## Arguments

* expression: numeric expression

## Return Type

Returns the standard deviation of the expression or NULL if there are no matching rows.

## Examples

The following table and values were used for the examples:

```sql
CREATE TABLE player_scores(player_name VARCHAR(50), player_id VARCHAR(10), 
    1st_qtr_score DECIMAL(5,2), 2nd_qtr_score DECIMAL(5,2), 
    3rd_qtr_score DECIMAL(5,2), 4th_qtr_score DECIMAL(5,2), 
    yearly_total AS 1st_qtr_score + 2nd_qtr_score + 3rd_qtr_score + 4th_qtr_score PERSISTED DECIMAL(5,2));

INSERT INTO player_scores VALUES
    ('Steve', '119','22.50','72.00', '63.00', '45.00'),
    ('Jack', '432', '90.10', '78.00','88.20', '92.20'),
    ('Jim', '779','75.00', '68.90','55.70', '72.00'), 
    ('Eve', '189','91.50', '88.10', '95.00', '94.50'),
    ('Shelia','338', '75.60', '72.00', '81.10', '78.40'),
    ('June', '521', '81.00', '87.30','76.80','82.20'),
    ('Martin', '674','98.80', '95.10', '88.00', '96.40');

```

## Aggregate Function

```sql
SELECT STDDEV(yearly_total) FROM player_scores;


```

```output

+----------------------+
| STDDEV(yearly_total) |
+----------------------+
|            57.083158 |
+----------------------+
```

## Window Function

```sql
SELECT player_name, yearly_total, 
ROUND(stddev(yearly_total) OVER (ORDER BY player_name, yearly_total)) AS stddev
FROM player_scores
ORDER BY player_name;


```

```output

+-------------+--------------+--------+
| player_name | yearly_total | stddev |
+-------------+--------------+--------+
| Eve         |       369.10 |      0 |
| Jack        |       348.50 |     10 |
| Jim         |       271.60 |     42 |
| June        |       327.30 |     36 |
| Martin      |       378.30 |     38 |
| Shelia      |       307.10 |     37 |
| Steve       |       202.50 |     57 |
+-------------+--------------+--------+
```

## Window Frame Clause

```sql
SELECT player_name, yearly_total, 
ROUND(stddev(yearly_total) OVER (ORDER BY player_name, yearly_total ROWS UNBOUNDED PRECEDING)) AS stddev
FROM player_scores
ORDER BY player_name;


```

```output

+-------------+--------------+--------+
| player_name | yearly_total | stddev |
+-------------+--------------+--------+
| Eve         |       369.10 |      0 |
| Jack        |       348.50 |     10 |
| Jim         |       271.60 |     42 |
| June        |       327.30 |     36 |
| Martin      |       378.30 |     38 |
| Shelia      |       307.10 |     37 |
| Steve       |       202.50 |     57 |
+-------------+--------------+--------+
```

***

Modified at: September 6, 2024

Source: [/db/v9.1/reference/sql-reference/aggregate-functions/stddev/](https://docs.singlestore.com/db/v9.1/reference/sql-reference/aggregate-functions/stddev/)

(An index of the documentation is available at /llms.txt)