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

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Syntax

VAR_POP(<expression>)

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Parameters

ParameterDescriptionSupported input types
<expression>An expression producing numeric values for which to calculate the population variance.REAL, DOUBLE PRECISION

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Return Type

VAR_POP returns a result of type DOUBLE PRECISION.

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Special cases

  • If there are no non-NULL input values, 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 population variance of the grade values from the exams table, rounds the result to three decimal places, and returns it as variance:

SELECT ROUND(VAR_POP(grade), 3) as variance from exams;

Returns The previous code returns the following result:

variance (DOUBLE PRECISION)
0.274