# How the STDDEV() function works in Mariadb?

The `STDDEV()`

function, short for standard deviation, is a statistical measure used in MariaDB to quantify the amount of variation or dispersion in a set of values.

The `STDDEV()`

function, short for standard deviation, is a statistical measure used in MariaDB to quantify the amount of variation or dispersion in a set of values. It is a square root of the variance, providing insights into the data’s spread in relation to the mean.

## Syntax

The syntax for the MariaDB `STDDEV()`

function is as follows:

```
STDDEV(expression)
```

The `STDDEV()`

function accepts an `expression`

, which is typically a column containing numeric data. It returns the standard deviation of the numeric values as a double-precision floating-point number.

## Examples

### Example 1: Calculating Standard Deviation

This example calculates the standard deviation of a series of numbers.

```
SELECT STDDEV(column_name) FROM table_name;
```

The output for this statement will display the standard deviation of the values in `column_name`

.

### Example 2: Standard Deviation with Condition

Here, we calculate the standard deviation of values that satisfy a specific condition.

```
SELECT STDDEV(column_name) FROM table_name WHERE condition;
```

The output will show the standard deviation of the filtered set of values.

### Example 3: Standard Deviation of Grouped Data

This example demonstrates how to calculate the standard deviation for grouped data.

```
SELECT group_column, STDDEV(column_name) FROM table_name GROUP BY group_column;
```

The output will list the standard deviation for each group defined by `group_column`

.

### Example 4: Standard Deviation with NULL Values

In this example, we see how `STDDEV()`

handles NULL values in the dataset.

```
SELECT STDDEV(column_name) FROM table_name;
```

If `column_name`

contains NULL values, they will be ignored in the standard deviation calculation.

### Example 5: Standard Deviation of an Empty Set

This example shows the result of calculating the standard deviation of an empty set.

```
SELECT STDDEV(column_name) FROM table_name WHERE false_condition;
```

The output for this statement will be `NULL`

since no data meets the condition.

## Related Functions

Below are a few functions related to the MariaDB `STDDEV()`

function:

- MariaDB
`VARIANCE()`

function calculates the variance of a set of values. - MariaDB
`AVG()`

function computes the average value of a set of values.

## Conclusion

Understanding the `STDDEV()`

function is crucial for data analysis in MariaDB, as it provides a statistical foundation for understanding data variability. It is especially useful in fields such as finance, research, and any domain where data dispersion plays a key role in decision-making. When interpreting the results, it’s important to consider the context of the data and the implications of the standard deviation in relation to the mean.