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Computes the sample variance of all non-NULL numeric values produced by an expression. The sample variance measures the average of the squared differences from the sample mean, indicating how spread out the values are within a sample. For information about the population variance, which measures how spread out the values are within the full population, see VAR_POP. Alias: VARIANCE

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Syntax

{ VARIANCE | VAR_SAMP }(<expression>) [FILTER ([WHERE] <condition>)]

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Parameters

ParameterDescriptionSupported input types
<expression>An expression producing numeric values for which to calculate the sample variance.REAL, DOUBLE PRECISION
<condition>An optional boolean expression to filter rows used in aggregationBOOL

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Return Type

VAR_SAMP returns a result of type DOUBLE PRECISION.

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Special cases

  • If there is at most one non-NULL input value, the result is NULL.
  • If the input contains an Inf or NaN value, the result will be NaN.

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Example

The following code creates an exams table with a grade column of type DOUBLE PRECISION, and inserts five grade values into it: 
CREATE TABLE exams (grade DOUBLE PRECISION);
INSERT INTO exams VALUES (4.0), (3.7), (3.3), (2.7), (2.7);
The following code calculates the sample variance of the grade values from the exams table, rounds the result to three decimal places, and returns it as variance: 
SELECT ROUND(VAR_SAMP(grade), 3) as variance from exams;
Returns The previous code returns the following result:
variance (DOUBLE PRECISION)
0.342