Name
STDDEV_SAMP
Use STDDEV_SAMP to find the sample standard deviation within a group of numeric values.
ANSI SQL Standard Syntax
STDDEV_SAMP(numeric_expression
)
MySQL and PostgreSQL
MySQL and PostgreSQL support the ANSI SQL syntax.
Oracle
Oracle supports the standard syntax. It also provides the STDDEV function, which operates similarly to STDDEV_SAMP except that it returns zero (instead of NULL) when there is only one value in the set.
Oracle also supports analytic syntax:
STDDEV_SAMP(numeric_expression
) OVER (window_clause
)
For an explanation of the window_clause
, see the section later in this chapter titled “ANSI SQL Window Functions.”
SQL Server
Use STDEV (with only one D!).
Example
The following example computes the sample standard deviation for the values 1, 2, and 3:
SELECT * FROM test;
X ---------- 1 2 3SELECT STDDEV_SAMP(x) FROM test;
STDDEV_SAMP(X) -------------- 1
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