STDDEV_SAMP

Computes the sample standard deviation of all non-NULL numeric values produced by an expression. The sample standard deviation measures how spread out values are in a sample by calculating the square root of the average of squared deviations from the sample mean, using a correction for sample size. For information about the population standard deviation, which estimates the spread of values in the full population, see STDDEV_POP. Alias: STDDEV

Syntax

{ STDDEV | STDDEV_SAMP }(<expression>) [FILTER ([WHERE] <condition>)]

Parameters

Parameter	Description	Supported input types
`<expression>`	An expression producing numeric values for which to calculate the sample standard deviation.	`REAL`, `DOUBLE PRECISION`
`<condition>`	An optional boolean expression to filter rows used in aggregation	`BOOL`

Return Type

STDDEV_SAMP returns a result of type DOUBLE PRECISION.

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.

Example

The following example calculates the sample standard deviation of five grade values:

SELECT ROUND(STDDEV_SAMP(grade::double precision), 3) AS stddev
FROM UNNEST(ARRAY[4.0, 3.7, 3.3, 2.7, 2.7]) AS t(grade);

stddev double null
0.585

Rows: 1Execution time: 6.55ms

STDDEV_POP

STRING_AGG

⌘I

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Syntax

Parameters

Return Type

Special cases

Example

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​Example

Syntax

Parameters

Return Type

Special cases

Example