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 Mathematical 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
The 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;
MySQL STDDEV_SAMP Group By Example
In general, we use STDDEV_SAMP function to calculate the Sample Standard Deviation of a products belongs to a 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 this 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 MySQL Query will group the Customers by their Profession, and calculates their Sample Standard Deviation
For this demonstration, we are taking Software Developer profession, and show you the output.
— Calculating the MySQL Mean
Mean = (70,000 + 79000) / 2
Mean = 74,500
— Calculating the MySQL Sample Variance
Sample Variance = ( (70,000 – 74500)² + (79000 – 74500) )² / (2 -1)
Sample Variance = 40,500,000
— Calculating MySQL Sample Standard Deviation
Sample Standard Deviation = SQRT (Variance)
Sample Standard Deviation = SQRT (40,500,000)
which means, Sample Standard Deviation = 6363.96
Thank You for Visiting Our Blog