MySQL VAR_SAMP Aggregate Function is useful for calculating the Sample Variance of total records (or rows) selected by the SELECT Statement.
The mathematical formula behind the VAR_SAMP to calculate the sample var is
--Calculating 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)
The syntax behind the VAR_SAMP function is
-- Syntax SELECT VAR_SAMP(Column_Name) FROM Source;
How to write VAR_SAMP function to calculate the sample Variance with an example using the below-shown data?.
MySQL VAR_SAMP Example
The VAR_SAMP function returns the Simple Variance of total records present in a specified column. For example, the below query calculates the same of all the records present in Yearly_Income from the Customer details table.
-- VAR_SAMP example SELECT VAR_SAMP(Yearly_Income) AS `Simple income Variance` FROM customerdetails;
Group By Example
In general, the MySQL VAR_SAMP function calculates the Sample Variance of products belonging to a particular category or color, etc.
USE company; SELECT Profession, VAR_SAMP(Yearly_Income) FROM customerdetails GROUP BY Profession;
The above SELECT Statement query group the Customers by their Profession and calculates their Sample Variance
We are taking the Software Developer profession and showing you the output.
— Calculating Mean
Mean = (70000 + 79,000) / 2
Mean = 74,500
Here, we are calculating Sample Variance.
Variance = (70,000 – 74,500)² + (79,000 – 74,500)² / (2-1)