MySQL STDDEV_SAMP is one of the Aggregate Function, which is used to calculate the Sample Standard Deviation of total records (or rows) selected by the SELECT Statement.

## MySQL STDDEV_SAMP Formula

The math formula behind STDDEV_SAMP to calculate the sample standard deviation in MySQL is as shown below:

--Calculating the Mean or Average Mean = Sum of each individual / Total number of items --Calculating the Sample Variance Sample Variance = ((OriginalValue – Mean)² + (OriginalValue – Mean)² +.... )/( Total number of items - 1) --Calculating Sample Standard Deviation Sample Standard Deviation = Square root (Sample Variance)

### MySQL STDDEV_SAMP Syntax

The basic syntax behind the STDDEV_SAMP in MySQL is as shown below:

-- MySQL STDDEV_SAMP example SELECT STDDEV_SAMP(Column_Name) FROM Source;

In this article we will show you, How to write STDDEV_SAMP function in MySQL to calculate Sample Standard Deviation with example. For this, We are going to use the below shown data

## MySQL STDDEV_SAMP Example

In MySQL Server, STDDEV_SAMP function will returns Sample Standard Deviation of total records present in a specified column. For example, below query will calculate the Sample Standard Deviation of total records present in Yearly_Income from Customer details table.

-- MySQL STDDEV_SAMP example SELECT STDDEV_SAMP(Yearly_Income) AS `Sample Standard Deviation` FROM customerdetails;

**OUTPUT**

## MySQL STDDEV_SAMP – Group By Example

In general, we use STDDEV_SAMP function to calculate the Sample Standard Deviation of a products belongs to particular category or color etc. In this situation we use GROUP BY Clause to group the products by color or some thing like that. And then we use STDDEV_SAMP Function to calculate the Sample Standard Deviation. Let us see the Example

-- MySQL STDDEV_SAMP Function Example USE company; SELECT Profession, STDDEV_SAMP(Yearly_Income), FROM customerdetails GROUP BY Profession;

Above SQL Query will group the Customers by their Profession, and calculates their Sample Standard Deviation

**OUTPUT**

**ANALYSIS**

We are taking Software Developer profession, and show you the output.

–Calculating Mean

Mean = (70,000 + 79000) / 2

Mean = 74,500

–Calculating Sample Variance

Sample Variance = ( (70,000 – 74500)² + (79000 – 74500) )² / (2 -1)

Sample Variance = 40,500,000

–Calculating Sample Standard Deviation

Sample Standard Deviation = SQRT (Variance)

Sample Standard Deviation = SQRT (40,500,000)

which means, Sample Standard Deviation = 6363.96

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