STDDEV_SAMP [Aggregate]

Evaluates the statistical sample standard deviation for each member of the group. The return value is the same as the square root of VAR_SAMP:

STDDEV_SAMP(expression) = SQRT(VAR_SAMP(expression))

Behavior Type

Immutable

Syntax

STDDEV_SAMP ( expression )

Parameters

expression

Any NUMERIC data type or any non-numeric data type that can be implicitly converted to a numeric data type. STDDEV_SAMP returns the same data type as expression.

Related Functions

  • STDDEV_SAMP is semantically identical to nonstandard function STDDEV, which is provided for compatibility with other databases.
  • This aggregate function differs from analytic function STDDEV_SAMP, which computes the statistical sample standard deviation of the current row with respect to the group of rows within a window.

  • When VAR_SAMP returns NULL, STDDEV_SAMP returns NULL.

Examples

The following example returns the statistical sample standard deviation for each household ID from the customer dimension table.

=> SELECT STDDEV_SAMP(household_id) FROM customer_dimension;
   stddev_samp    
------------------
 8651.50842400771
(1 row)